1929Hotelling - Stability in Competition
nominal rigidities and the dynamic effects of a shock to monetary policy

Nominal Rigidities and the Dynamic Effects of a Shockto Monetary Policy∗Lawrence J.Christiano†Martin Eichenbaum‡Charles L.Evans§August27,2003AbstractWe present a model embodying moderate amounts of nominal rigidities that ac-counts for the observed inertia in inflation and persistence in output.The key featuresof our model are those that prevent a sharp rise in marginal costs after an expansion-ary shock to monetary policy.Of these features,the most important are staggeredwage contracts which have an average duration of three quarters,and variable capitalutilization.JEL:E3,E4,E5∗Thefirst two authors are grateful for thefinancial support of a National Science Foundation grant to the National Bureau of Economic Research.We would like to acknowledge helpful comments from Lars Hansen and Mark Watson.We particularly want to thank Levon Barseghyan for his superb research assistance,as well as his insightful comments on various drafts of the paper.This paper does not necessarily reflect the views of the Federal Reserve Bank of Chicago or the Federal Reserve System.†Northwestern University,National Bureau of Economic Research,and Federal Reserve Banks of Chicago and Cleveland.‡Northwestern University,National Bureau of Economic Research,and Federal Reserve Bank of Chicago.§Federal Reserve Bank of Chicago.1.IntroductionThis paper seeks to understand the observed inertial behavior of inflation and persistence in aggregate quantities.To this end,we formulate and estimate a dynamic,general equilibrium model that incorporates staggered wage and price contracts.We use our model to investigate what mix of frictions can account for the evidence of inertia and persistence.For this exercise to be well defined,we must characterize inertia and persistence precisely.We do so using estimates of the dynamic response of inflation and aggregate variables to a monetary policy shock.With this characterization,the question that we ask reduces to:‘Can models with moderate degrees of nominal rigidities generate inertial inflation and persistent output movements in response to a monetary policy shock?’1Our answer to this question is,‘yes’.The model that we construct has two key features.First,it embeds Calvo style nominal price and wage contracts.Second,the real side of the model incorporates four departures from the standard textbook one sector dynamic stochastic growth model.These depar-tures are motivated by recent research on the determinants of consumption,asset prices, investment and productivity.The specific departures that we include are habit formation in preferences for consumption,adjustment costs in investment and variable capital utilization. In addition,we assume thatfirms must borrow working capital tofinance their wage bill.Our keyfindings are as follows.First,the average duration of price and wage contracts in the estimated model is roughly2and3quarters,respectively.Despite the modest nature of these nominal rigidities,the model does a very good job of accounting quantitatively for the estimated response of the US economy to a policy shock.In addition to reproducing the dynamic response of inflation and output,the model also accounts for the delayed,hump-shaped response in consumption,investment,profits,productivity and the weak response of the real wage.2Second,the critical nominal friction in our model is wage contracts,not price contracts.A version of the model with only nominal wage rigidities does almost as well as the estimated model.In contrast,with only nominal price rigidities,the model performs very poorly.Consistent with existing results in the literature,this version of the model cannot generate persistent movements in output unless we assume price contracts of extremely long duration.The model with only nominal wage rigidities does not have this problem.Third,we document how inference about nominal rigidities varies across different spec-ifications of the real side of our model.3Estimated versions of the model that do not in-1This question that is the focus of a large and growing literature.See,for example,Chari,Kehoe and McGrattan(2000),Mankiw(2001),Rotemberg and Woodford(1999)and the references therein.2In related work,Sbordone(2000)argues that,taking as given aggregate real variables,a model with staggered wages and prices does well at accounting for the time series properties of wages and prices.See also Ambler,Guay and Phaneuf(1999)and Huang and Liu(2002)for interesting work on the role of wage contracts.3For early discussions about the impact of real frictions on the effects of nominal rigidities,see Blanchardcorporate our departures from the standard growth model imply implausibly long price and wage contracts.Fourth,wefind that if one only wants to generate inertia in inflation and persistence in output with moderate wage and price stickiness,then it is crucial to allow for variable capital utilization.To understand why this feature is so important,note that in our modelfirms set prices as a markup over marginal costs.The major components of marginal costs are wages and the rental rate of capital.By allowing the services of capital to increase after a positive monetary policy shock,variable capital utilization helps dampen the large rise in the rental rate of capital that would otherwise occur.This in turn dampens the rise in marginal costs and,hence,prices.The resulting inertia in inflation implies that the rise in nominal spending that occurs after a positive monetary policy shock produces a persistent rise in real output.Similar intuition explains why sticky wages play a critical role in allowing our model to explain inflation inertia and output persistence.It also explains why our assumption about working capital plays a useful role:other things equal,a decline in the interest rate lowers marginal cost.Fifth,although investment adjustment costs and habit formation do not play a central role with respect to inflation inertia and output persistence,they do play a critical role in accounting for the dynamics of other variables.Sixth,the major role played by the working capital channel is to reduce the model’s reliance on sticky prices.Specifically,if we estimate a version of the model that does not allow for this channel,the average duration of price contracts increases dramatically.Finally,wefind that our model embodies strong internal propagation mechanisms.The impact of a monetary policy shock on aggregate activity continues to grow and persist even beyond the time when the typical contract in place at the time of the shock is reoptimized.In addition,the effects persist well beyond the effects of the shock on the interest rate and the growth rate of money.We pursue a particular limited information econometric strategy to estimate and evaluate our model.To implement this strategy wefirst estimate the impulse response of eight key macroeconomic variables to a monetary policy shock using an identified vector autoregres-sion(V AR).We then choose six model parameters to minimize the difference between the estimated impulse response functions and the analogous objects in our model.4 The remainder of this paper is organized as follows.In section2we briefly describe our estimates of how the U.S.economy responds to a monetary policy shock.Section3 displays our economic model.In Section4we discuss our econometric methodology.Our empirical results are reported in Section5and analyzed in Section6.Concluding commentsand Fisher(1989),Ball and Romer(1990)and Romer(1996).For more recent quantitative discussions, see Chari,Kehoe and McGrattan(2000),Edge(2000),Fuhrer(2000),Kiley(1997),McCallum and Nelson (1998)and Sims(1998).4Christiano,Eichenbaum and Evans(1998),Edge(2000)and Rotemberg and Woodford(1997)have also applied this strategy in the context of monetary policy shocks.are contained in Section7.2.The Consequences of a Monetary Policy ShockThis section begins by describing how we estimate a monetary policy shock.We then re-port estimates of how major macroeconomic variables respond to a monetary policy shock. Finally,we report the fraction of the variance in these variables that is accounted for by monetary policy shocks.The starting point of our analysis is the following characterization of monetary policy:R t=f(Ωt)+εt.(2.1)Here,R t is the Federal Funds rate,f is a linear function,Ωt is an information set,andεt is the monetary policy shock.We assume that the Fed allows money growth to be whatever is necessary to guarantee that(2.1)holds.Our basic identifying assumption is thatεt is orthogonal to the elements inΩt.Below,we describe the variables inΩt and elaborate on the interpretation of this orthogonality assumption.We now discuss how we estimate the dynamic response of key macroecomomic variables to a monetary policy shock.Let Y t denote the vector of variables included in the analysis. We partition Y t as follows:Y t=[Y1t,R t,Y2t]0.The vector Y1t is composed of the variables whose time t elements are contained inΩt,and are assumed not to respond contemporaneously to a monetary policy shock.The vector Y2t consists of the time t values of all the other variables inΩt.The variables in Y1t are real GDP, real consumption,the GDP deflator,real investment,the real wage,and labor productivity. The variables in Y2t are real profits and the growth rate of M2.All these variables,except money growth,have been logged.We measure the interest rate,R t,using the Federal Funds rate.The data sources are in an appendix,available from the authors.With one exception(the growth rate of money)all the variables in Y t are include in levels.Altig,Christiano,Eichenbaum and Linde(2003)adopt an alternative specification of Y t,in which cointegrating relationships among the variables are imposed.For example,the growth rate of GDP and the log difference between labor productivity and the real wage are included.The key properties of the impulse responses to a monetary policy shock are insensitive to this alternative specification.The ordering of the variables in Y t embodies two key identifying assumptions.First,the variables in Y1t do not respond contemporaneously to a monetary policy shock.Second,the time t information set of the monetary authority consists of current and lagged values of the variables in Y1t and only past values of the variables in Y2t.Our decision to include all variables,except for the growth rate of M2and real profits in Y1t,reflects a long-standing view that macroeconomic variables do not respond instanta-neously to policy shocks(see Friedman(1968)).We refer the reader to Christiano,Eichen-baum and Evans(1999)for a discussion of sensitivity of inference to alternative assumptions about the variables included in Y1t.While our assumptions are certainly debatable,the anal-ysis is internally consistent in the sense that we make the same assumptions in our economic model.To maintain consistency with the model,we place profits and the growth rate of money in Y2t.The V AR contains4lags of each variable and the sample period is1965Q3-1995Q3.5 Ignoring the constant term,the V AR can be written as follows:Y t=A1Y t−1+...+A4Y t−4+Cηt,(2.2)where C is a9×9lower triangular matrix with diagonal terms equal to unity,andηt is a9−dimensional vector of zero-mean,serially uncorrelated shocks with diagonal variance-covariance matrix.Since there are six variables in Y1t,the monetary policy shock,εt,is the7th element ofηt.A positive shock toεt corresponds to a contractionary monetary policy shock. We estimate the parameters-A i,i=1,...,4,C,and the variances of the elements ofηt-using standard least squares ing these estimates,we compute the dynamic path of Y t following a one-standard-deviation shock inεt,setting initial conditions to zero.This path, which corresponds to the coefficients in the impulse response functions of interest,is invariant to the ordering of the variables within Y1t and within Y2t(see Christiano,Eichenbaum and Evans(1999).)The impulse response functions of all variables in Y t are displayed in Figure1.Lines marked‘+’correspond to the point estimates.The shaded areas indicate95%confidence intervals about the point estimates.6The solid lines pertain to the properties of our structural model,which will be discussed in section3.The results suggest that after an expansionary monetary policy shock there is a:•hump-shaped response of output,consumption and investment,with the peak effect occurring after about1.5years and returning to their pre-shock levels after about three years,•hump-shaped response in inflation,with a peak response after about2years,•fall in the interest rate for roughly one year,•rise in profits,real wages and labor productivity,and5This sample period is the same as in Christiano,Eichenbaum and Evans(1999).6We use the method described in Sims and Zha(1999).•an immediate rise in the growth rate of money.Interestingly,these results are consistent with the claims in Friedman(1968).For example, Friedman argued that an exogenous increase in the money supply leads to a drop in the interest rate that lasts one to two years,and a rise in output and employment that lasts from two tofive years.Finally,the robustness of the qualitative features of ourfindings to alternative identifying assumptions and sample sub-periods,as well as the use of monthly data,is discussed in Christiano,Eichenbaum and Evans(1999).Our strategy for estimating the parameters of our model focuses on only a component of thefluctuations in the data,namely the portion that is due to a monetary policy shock. It is natural to ask how large that component is,since ultimately we are interested in a model that can account for the variation in the data.With this question in mind,the following table reports variance decompositions.In particular,it displays the percent of the variance of the k−step forecast error in the elements of Y t due to monetary policy shocks, for k=4,8and20.Numbers in parentheses are the boundaries of the associated95% confidence interval.7Notice that policy shocks account for only a small fraction of inflation. At the same time,with the exception of real wages,monetary policy shocks account for a non-trivial fraction of the variation in the real variables.This last inference should be treated with caution.The confidence intervals about the point estimates are rather large. Also,while the impulse response functions are robust to the various perturbations discussed in Christiano,Eichenbaum and Evans(1999)and Altig,Christiano,Eichenbaum and Linde (2003),the variance decompositions can be sensitive.For example,the analogous point estimates reported in Altig,Christiano,Eichenbaum and Linde(2003)are substantially smaller than those reported in Table1.3.The Model EconomyIn this section we describe our model economy and display the problems solved byfirms and households.In addition,we describe the behavior offinancial intermediaries and the monetary andfiscal authorities.The only source of uncertainty in the model is a shock to monetary policy.7These confidence intervals are computed based on bootstrap simulations of the estimated VAR.In each artificial data set we computed the variance decompositions corresponding to the ones in Table1.The lower and upper bounds of the confidence intervals correspond to the2.5and97.5percentiles of simulated variance decompositions.3.1.Final Good FirmsAt time t,afinal consumption good,Y t,is produced by a perfectly competitive,representative firm.Thefirm produces thefinal good by combining a continuum of intermediate goods, indexed by j∈[0,1],using the technologyY t=·Z10Y jt1f dj¸λf(3.1) where1≤λf<∞and Y jt denotes the time t input of intermediate good j.Thefirm takes its output price,P t,and its input prices,P jt,as given and beyond its control.Profit maximization implies the Euler equationµP t jt¶λfλf−1=Y jt t.(3.2)Integrating(3.2)and imposing(3.1),we obtain the following relationship between the price of thefinal good and the price of the intermediate good:P t=·Z10P11−λf jt dj¸(1−λf).(3.3) 3.2.Intermediate Good FirmsIntermediate good j∈(0,1)is produced by a monopolist who uses the following technology:Y jt=½kαjt L1−αjt−φif kαjt L1−αjt≥φ0otherwise(3.4) where0<α<1.Here,L jt and k jt denote time t labor and capital services used to produce the j th intermediate good.Also,φ>0denotes thefixed cost of production.We rule out entry and exit into the production of intermediate good j.Intermediatefirms rent capital and labor in perfectly competitive factor markets.Profits are distributed to households at the end of each time period.Let R k t and W t denote the nominal rental rate on capital services and the wage rate,respectively.Workers must be paid in advance of production.As a result,the j thfirm must borrow its wage bill,W t L jt, from thefinancial intermediary at the beginning of the period.Repayment occurs at the end of time period t at the gross interest rate,R t.Thefirm’s real marginal cost iss t=∂S t(Y)∂Y,where S t(Y)=mink,l©r k t k+w t R t l,Y given by(3.4)ª,where r k t=R k t/P t and w t=W t/P t.Given our functional forms,we haves t=µ1¶1−αµ1¶α¡r k t¢α(w t R t)1−α.(3.5)Apart fromfixed costs,thefirm’s time t profits are:·P jt P t−s t¸P t Y jt,where P jt isfirm j’s price.We assume thatfirms set prices according to a variant of the mechanism spelled out in Calvo(1983).This model has been widely used to characterize price-setting frictions.A useful feature of the model is that it can be solved without explicitly tracking the distribution of prices acrossfirms.In each period,afirm faces a constant probability,1−ξp,of being able to reoptimize its nominal price.The ability to reoptimize its price is independent across firms and time.If afirm can reoptimize its price,it does so before the realization of the time t growth rate of money.Firms that cannot reoptimize their price simply index to lagged inflation:P jt=πt−1P j,t−1.(3.6) Here,πt=P t/P t−1.We refer to this price-setting rule as lagged inflation indexation.Let˜P t denote the value of P jt set by afirm that can reoptimize at time t.Our notation does not allow˜P t to depend on j.We do this in anticipation of the well known result that, in models like ours,allfirms who can reoptimize their price at time t choose the same price (see Woodford,1996and Yun,1996).Thefirm chooses˜P t to maximize:∞X l=0¡βξp¢lυt+l h˜P t X tl−s t+l P t+l i Y j,t+l,(3.7)E t−1subject to(3.2),(3.5)and.(3.8)X tl=½πt×πt+1×···×πt+l−1for l≥11l=0In(3.7),υt is the marginal value of a dollar to the household,which is treated as exogenous by thefiter,we show that the value of a dollar,in utility terms,is constant across households.Also,E t−1denotes the expectations operator conditioned on lagged growth rates of money,µt−l,l≥1.This specification of the information set captures our assumption that thefirm chooses˜P t before the realization of the time t growth rate of money.To understand (3.7),note that˜P t influencesfirm j’s profits only as long as it cannot reoptimize its price.The probability that this happens for l periods is¡ξp¢l,in which case P j,t+l=˜P t X tl.The presence of¡ξp¢l in(3.7)has the effect of isolating future realizations of idiosyncratic uncertainty in which˜P t continues to affect thefirm’s profits.3.3.HouseholdsThere is a continuum of households,indexed by j∈(0,1).The j th household makes a sequence of decisions during each period.First,it makes its consumption decision,its capital accumulation decision,and it decides how many units of capital services to supply.Second, it purchases securities whose payoffs are contingent upon whether it can reoptimize its wage decision.Third,it sets its wage rate afterfinding out whether it can reoptimize or not. Fourth,it receives a lump-sum transfer from the monetary authority.Finally,it decides how much of itsfinancial assets to hold in the form of deposits with afinancial intermediary and how much to hold in the form of cash.Since the uncertainty faced by the household over whether it can reoptimize its wage is idiosyncratic in nature,households work different amounts and earn different wage rates.So, in principle,they are also heterogeneous with respect to consumption and asset holdings.A straightforward extension of arguments in Erceg,Henderson and Levin(2000)and Woodford (1996)establish that the existence of state contingent securities ensures that,in equilibrium, households are homogeneous with respect to consumption and asset holdings.Reflecting this result,our notation assumes that households are homogeneous with respect to consumption and asset holdings but heterogeneous with respect to the wage rate that they earn and hours worked.The preferences of the j th household are given by:∞X l=0βl−t[u(c t+l−bc t+l−1)−z(h j,t+l)+v(q t+l)].(3.9)E j t−1Here,E j t−1is the expectation operator,conditional on aggregate and household j idiosyn-cratic information up to,and including,time t−1;c t denotes time t consumption;h jt denotes time t hours worked;q t≡Q t/P t denotes real cash balances;Q t denotes nominal cash balances.When b>0,(3.9)allows for habit formation in consumption preferences.The household’s asset evolution equation is given by:M t+1=R t[M t−Q t+(µt−1)M a t]+A j,t+Q t+W j,t h j,t(3.10)+R k t u t¯k t+D t−P t¡i t+c t+a(u t)¯k t¢.Here,M t is the household’s beginning of period t stock of money and W j,t h j,t is time t labor income.In addition,¯k t,D t and A j,t denote,respectively,the physical stock of capital,firm profits and the net cash inflow from participating in state-contingent securities at time t. The variableµt represents the gross growth rate of the economy-wide per capita stock of money,M a t.The quantity(µt−1)M a t is a lump-sum payment made to households by the monetary authority.The quantity M t−P t q t+(µt−1)M a t,is deposited by the household with afinancial intermediary where it earns the gross nominal rate of interest,R t.The remaining terms in(3.10),aside from P t c t,pertain to the stock of installed capital, which we assume is owned by the household.The household’s stock of physical capital,¯k t, evolves according to:¯k=(1−δ)¯k t+F(i t,i t−1).(3.11)t+1Here,δdenotes the physical rate of depreciation and i t denotes time t purchases of invest-ment goods.The function,F,summarizes the technology that transforms current and past investment into installed capital for use in the following period.We discuss the properties of F below.Capital services,k t,are related to the physical stock of capital byk t=u t¯k t.Here,u t denotes the utilization rate of capital,which we assume is set by the household.8 In(3.10),R k t u t¯k t represents the household’s earnings from supplying capital services.The increasing,convex function a(u t)¯k t denotes the cost,in units of consumption goods,of setting the utilization rate to u t.3.4.The W age DecisionAs in Erceg,Henderson and Levin(2000),we assume that the household is a monopoly sup-plier of a differentiated labor service,h jt.It sells this service to a representative,competitive firm that transforms it into an aggregate labor input,L t,using the following technology:L t=·Z10h1λjt dj¸λw.The demand curve for h jt is given by:h jt=µW t jt¶λwλw−1L t,1≤λw<∞.(3.12) Here,W t is the aggregate wage rate,i.e.,the price of L t.It is straightforward to show that W t is related to W jt via the relationship:W t=·Z10(W jt)11−λw dj¸1−λw.(3.13) The household takes L t and W t as given.8Our assumption that households make the capital accumulation and utilization decisions is a matter of convenience.At the cost of a more complicated notation,we could work with an alternative decentralization scheme in whichfirms make these decisions.Households set their wage rate according to a variant of the mechanism used to model price setting byfirms.In each period,a household faces a constant probability,1−ξw, of being able to reoptimize its nominal wage.The ability to reoptimize is independent across households and time.If a household cannot reoptimize its wage at time t,it sets W jt according to:W j,t=πt−1W j,t−1.(3.14) 3.5.Monetary and Fiscal PolicyWe assume that monetary policy is given by:µt=µ+θ0εt+θ1εt−1+θ2εt−2+...(3.15)Here,µdenotes the mean growth rate of money andθj is the response of E tµt+j to a time t monetary policy shock.We assume that the government has access to lump sum taxes and pursues a Ricardianfiscal policy.Under this type of policy,the details of tax policy have no impact on inflation and other aggregate economic variables.As a result,we need not specify the details offiscal policy.93.6.Loan Market Clearing,Final Goods Clearing and EquilibriumFinancial intermediaries receive M t−Q t from households and a transfer,(µt−1)M t from the monetary authority.Our notation here reflects the equilibrium condition,M a t=M t. Financial intermediaries lend all of their money to intermediate goodfirms,which use the funds to pay for L t.Loan market clearing requiresW t L t=µt M t−Q t.(3.16) The aggregate resource constraint isc t+i t+a(u t)≤Y t.We adopt a standard sequence-of-markets equilibrium concept.In the appendix we discuss our computational strategy for approximating that equilibrium.This strategy involves taking a linear approximation about the non-stochastic steady state of the economy and using the solution method discussed in Christiano(2003).For details,see the previous version of this paper,Christiano,Eichenbaum and Evans(2001).In principle,the non-negativity constraint on intermediate good output in(3.4)is a problem for this approximation.It turns out that the constraint is not binding for the experiments that we consider and so we ignore it.Finally, it is worth noting that since profits are stochastic,the fact that they are zero,on average, 9See Sims(1994)or Woodford(1994)for a further discussion.implies that they are often negative.As a consequence,our assumption thatfirms cannot exit is binding.Allowing forfirm entry and exit dynamics would considerably complicate our analysis.3.7.Functional Form AssumptionsWe assume that the functions characterizing utility are given by:u(·)=log(·)z(·)=ψ0(·)2.(3.17)v(·)=ψq(·)1−σqqIn addition,investment adjustment costs are given by:F(i t,i t−1)=(1−Sµi t i t−1¶)i t.(3.18) We restrict the function S to satisfy the following properties:S(1)=S0(1)=0,andκ≡S00(1)>0.It is easy to verify that the steady state of the model does not depend on the adjustment cost parameter,κ.Of course,the dynamics of the model are influenced byκ. Given our solution procedure,no other features of the S function need to be specified for our analysis.We impose two restrictions on the capital utilization function,a(u t).First,we require that u t=1in steady state.Second,we assume a(1)=0.Under our assumptions,the steady state of the model is independent ofσa=a00(1)/a0(1).The dynamics do depend onσa.Given our solution procedure,we do not need to specify any other features of the function a. 4.Econometric MethodologyIn this section we discuss our methodology for estimating and evaluating our model.We partition the model parameters into three groups.Thefirst group is composed ofβ,φ,α,δ,ψ0,ψq,λw andµ.We setβ=1.03−0.25,which implies a steady state annualized real interest rate of3percent.We setα=0.36,which corresponds to a steady state share of capital income equal to roughly36percent.We setδ=0.025,which implies an annual rate of depreciation on capital equal to10percent.This value ofδis roughly equal to the estimate reported in Christiano and Eichenbaum(1992).The parameter,φ,is set to guarantee that profits are zero in steady state.This value is consistent with Basu and Fernald(1994),Hall (1988),and Rotemberg and Woodford(1995),who argue that economic profits are close to zero on average.Although there are well known problems with the measurement of profits, we think that zero profits is a reasonable benchmark.。
Hotelling模型再探讨

Hotelling模型再探讨本文修改Hotelling(1929)模型的基本假定,假定厂商边际生产成本为正,交通成本由消费者负担,厂商区位可以为内生变量,也可以为外生变量,在此假定前提下,分析厂商的最优的区位——价格策略,以探讨最大差异原则或者最小差异化原则何时成立,或者不成立。
标签:最大差异化最小差异化区位内生区位外生一、绪论Hotelling(1929年)最早使用线性区位模型研究了厂商间空间竞争的问题。
假定厂商的边际生产成本为零,在利润最大化假设下,其结论为两厂商会同时在城市中点的位置进行选址,即最小差异化原则。
D.Aspremont、Gabszewicz 与Thisse(1979年)延续其构想,但对其假设加以修正,却得到截然不同的结果。
在Bertrand竞争(价格竞争)下,两厂商聚集在中心点会使均衡价格为零,故两厂商必会在线形城市的两个不同端点选址,即最大差异化原则。
此后,关于最大差异化原则和最小差异化原则何者成立或者不成立的问题引起了广泛的讨论。
在Hotelling(1929年)和D’Aspremont,Gabszewicz and Thisse(1979年)的模型内,有两个重要的假设值得讨论。
第一,消费者所负担的单位交通成本相同。
这一假设与实际的情形可能不符。
比如排队购买,消费者宁愿多花时间购买某一产品而不购买对手的产品,这相当于提高了消费者的单位旅行成本。
又比如,厂商的服务效率不同,也会影响消费者的单位交通成本。
第二,厂商边际生产成本为零。
这在现实生活中是比较少见的。
因此,如果上述假设不成立,厂商的区位——价格策略发生何种变化,这是本文要探讨的第一个问题。
此外,研究厂商区位选择的文献,多假定厂商的区位内生变量,即通常假定厂商进行两个阶段的博弈,这又可以分为两种情况:两厂商同时选址,此后同时制定价格,即完全信息静态博弈;两厂商先后进入市场,后进入市场的厂商在观察到先进入市场的厂商选择后再进入市场,即完全信息动态博弈。
最近鲁棒优化进展Recent Advances in Robust Optimization and Robustness An Overview

Recent Advances in Robust Optimization and Robustness:An OverviewVirginie Gabrel∗and C´e cile Murat†and Aur´e lie Thiele‡July2012AbstractThis paper provides an overview of developments in robust optimization and robustness published in the aca-demic literature over the pastfive years.1IntroductionThis review focuses on papers identified by Web of Science as having been published since2007(included),be-longing to the area of Operations Research and Management Science,and having‘robust’and‘optimization’in their title.There were exactly100such papers as of June20,2012.We have completed this list by considering 726works indexed by Web of Science that had either robustness(for80of them)or robust(for646)in their title and belonged to the Operations Research and Management Science topic area.We also identified34PhD disserta-tions dated from the lastfive years with‘robust’in their title and belonging to the areas of operations research or management.Among those we have chosen to focus on the works with a primary focus on management science rather than system design or optimal control,which are broadfields that would deserve a review paper of their own, and papers that could be of interest to a large segment of the robust optimization research community.We feel it is important to include PhD dissertations to identify these recent graduates as the new generation trained in robust optimization and robustness analysis,whether they have remained in academia or joined industry.We have also added a few not-yet-published preprints to capture ongoing research efforts.While many additional works would have deserved inclusion,we feel that the works selected give an informative and comprehensive view of the state of robustness and robust optimization to date in the context of operations research and management science.∗Universit´e Paris-Dauphine,LAMSADE,Place du Mar´e chal de Lattre de Tassigny,F-75775Paris Cedex16,France gabrel@lamsade.dauphine.fr Corresponding author†Universit´e Paris-Dauphine,LAMSADE,Place du Mar´e chal de Lattre de Tassigny,F-75775Paris Cedex16,France mu-rat@lamsade.dauphine.fr‡Lehigh University,Industrial and Systems Engineering Department,200W Packer Ave Bethlehem PA18015,USA aure-lie.thiele@2Theory of Robust Optimization and Robustness2.1Definitions and BasicsThe term“robust optimization”has come to encompass several approaches to protecting the decision-maker against parameter ambiguity and stochastic uncertainty.At a high level,the manager must determine what it means for him to have a robust solution:is it a solution whose feasibility must be guaranteed for any realization of the uncertain parameters?or whose objective value must be guaranteed?or whose distance to optimality must be guaranteed? The main paradigm relies on worst-case analysis:a solution is evaluated using the realization of the uncertainty that is most unfavorable.The way to compute the worst case is also open to debate:should it use afinite number of scenarios,such as historical data,or continuous,convex uncertainty sets,such as polyhedra or ellipsoids?The answers to these questions will determine the formulation and the type of the robust counterpart.Issues of over-conservatism are paramount in robust optimization,where the uncertain parameter set over which the worst case is computed should be chosen to achieve a trade-off between system performance and protection against uncertainty,i.e.,neither too small nor too large.2.2Static Robust OptimizationIn this framework,the manager must take a decision in the presence of uncertainty and no recourse action will be possible once uncertainty has been realized.It is then necessary to distinguish between two types of uncertainty: uncertainty on the feasibility of the solution and uncertainty on its objective value.Indeed,the decision maker generally has different attitudes with respect to infeasibility and sub-optimality,which justifies analyzing these two settings separately.2.2.1Uncertainty on feasibilityWhen uncertainty affects the feasibility of a solution,robust optimization seeks to obtain a solution that will be feasible for any realization taken by the unknown coefficients;however,complete protection from adverse realiza-tions often comes at the expense of a severe deterioration in the objective.This extreme approach can be justified in some engineering applications of robustness,such as robust control theory,but is less advisable in operations research,where adverse events such as low customer demand do not produce the high-profile repercussions that engineering failures–such as a doomed satellite launch or a destroyed unmanned robot–can have.To make the robust methodology appealing to business practitioners,robust optimization thus focuses on obtaining a solution that will be feasible for any realization taken by the unknown coefficients within a smaller,“realistic”set,called the uncertainty set,which is centered around the nominal values of the uncertain parameters.The goal becomes to optimize the objective,over the set of solutions that are feasible for all coefficient values in the uncertainty set.The specific choice of the set plays an important role in ensuring computational tractability of the robust problem and limiting deterioration of the objective at optimality,and must be thought through carefully by the decision maker.A large branch of robust optimization focuses on worst-case optimization over a convex uncertainty set.The reader is referred to Bertsimas et al.(2011a)and Ben-Tal and Nemirovski(2008)for comprehensive surveys of robust optimization and to Ben-Tal et al.(2009)for a book treatment of the topic.2.2.2Uncertainty on objective valueWhen uncertainty affects the optimality of a solution,robust optimization seeks to obtain a solution that performs well for any realization taken by the unknown coefficients.While a common criterion is to optimize the worst-case objective,some studies have investigated other robustness measures.Roy(2010)proposes a new robustness criterion that holds great appeal for the manager due to its simplicity of use and practical relevance.This framework,called bw-robustness,allows the decision-maker to identify a solution which guarantees an objective value,in a maximization problem,of at least w in all scenarios,and maximizes the probability of reaching a target value of b(b>w).Gabrel et al.(2011)extend this criterion from afinite set of scenarios to the case of an uncertainty set modeled using intervals.Kalai et al.(2012)suggest another criterion called lexicographicα-robustness,also defined over afinite set of scenarios for the uncertain parameters,which mitigates the primary role of the worst-case scenario in defining the solution.Thiele(2010)discusses over-conservatism in robust linear optimization with cost uncertainty.Gancarova and Todd(2012)studies the loss in objective value when an inaccurate objective is optimized instead of the true one, and shows that on average this loss is very small,for an arbitrary compact feasible region.In combinatorial optimization,Morrison(2010)develops a framework of robustness based on persistence(of decisions)using the Dempster-Shafer theory as an evidence of robustness and applies it to portfolio tracking and sensor placement.2.2.3DualitySince duality has been shown to play a key role in the tractability of robust optimization(see for instance Bertsimas et al.(2011a)),it is natural to ask how duality and robust optimization are connected.Beck and Ben-Tal(2009) shows that primal worst is equal to dual best.The relationship between robustness and duality is also explored in Gabrel and Murat(2010)when the right-hand sides of the constraints are uncertain and the uncertainty sets are represented using intervals,with a focus on establishing the relationships between linear programs with uncertain right hand sides and linear programs with uncertain objective coefficients using duality theory.This avenue of research is further explored in Gabrel et al.(2010)and Remli(2011).2.3Multi-Stage Decision-MakingMost early work on robust optimization focused on static decision-making:the manager decided at once of the values taken by all decision variables and,if the problem allowed for multiple decision stages as uncertainty was realized,the stages were incorporated by re-solving the multi-stage problem as time went by and implementing only the decisions related to the current stage.As thefield of static robust optimization matured,incorporating–ina tractable manner–the information revealed over time directly into the modeling framework became a major area of research.2.3.1Optimal and Approximate PoliciesA work going in that direction is Bertsimas et al.(2010a),which establishes the optimality of policies affine in the uncertainty for one-dimensional robust optimization problems with convex state costs and linear control costs.Chen et al.(2007)also suggests a tractable approximation for a class of multistage chance-constrained linear program-ming problems,which converts the original formulation into a second-order cone programming problem.Chen and Zhang(2009)propose an extension of the Affinely Adjustable Robust Counterpart framework described in Ben-Tal et al.(2009)and argue that its potential is well beyond what has been in the literature so far.2.3.2Two stagesBecause of the difficulty in incorporating multiple stages in robust optimization,many theoretical works have focused on two stages.Regarding two-stage problems,Thiele et al.(2009)presents a cutting-plane method based on Kelley’s algorithm for solving convex adjustable robust optimization problems,while Terry(2009)provides in addition preliminary results on the conditioning of a robust linear program and of an equivalent second-order cone program.Assavapokee et al.(2008a)and Assavapokee et al.(2008b)develop tractable algorithms in the case of robust two-stage problems where the worst-case regret is minimized,in the case of interval-based uncertainty and scenario-based uncertainty,respectively,while Minoux(2011)provides complexity results for the two-stage robust linear problem with right-hand-side uncertainty.2.4Connection with Stochastic OptimizationAn early stream in robust optimization modeled stochastic variables as uncertain parameters belonging to a known uncertainty set,to which robust optimization techniques were then applied.An advantage of this method was to yield approaches to decision-making under uncertainty that were of a level of complexity similar to that of their deterministic counterparts,and did not suffer from the curse of dimensionality that afflicts stochastic and dynamic programming.Researchers are now making renewed efforts to connect the robust optimization and stochastic opti-mization paradigms,for instance quantifying the performance of the robust optimization solution in the stochastic world.The topic of robust optimization in the context of uncertain probability distributions,i.e.,in the stochastic framework itself,is also being revisited.2.4.1Bridging the Robust and Stochastic WorldsBertsimas and Goyal(2010)investigates the performance of static robust solutions in two-stage stochastic and adaptive optimization problems.The authors show that static robust solutions are good-quality solutions to the adaptive problem under a broad set of assumptions.They provide bounds on the ratio of the cost of the optimal static robust solution to the optimal expected cost in the stochastic problem,called the stochasticity gap,and onthe ratio of the cost of the optimal static robust solution to the optimal cost in the two-stage adaptable problem, called the adaptability gap.Chen et al.(2007),mentioned earlier,also provides a robust optimization perspective to stochastic programming.Bertsimas et al.(2011a)investigates the role of geometric properties of uncertainty sets, such as symmetry,in the power offinite adaptability in multistage stochastic and adaptive optimization.Duzgun(2012)bridges descriptions of uncertainty based on stochastic and robust optimization by considering multiple ranges for each uncertain parameter and setting the maximum number of parameters that can fall within each range.The corresponding optimization problem can be reformulated in a tractable manner using the total unimodularity of the feasible set and allows for afiner description of uncertainty while preserving tractability.It also studies the formulations that arise in robust binary optimization with uncertain objective coefficients using the Bernstein approximation to chance constraints described in Ben-Tal et al.(2009),and shows that the robust optimization problems are deterministic problems for modified values of the coefficients.While many results bridging the robust and stochastic worlds focus on giving probabilistic guarantees for the solutions generated by the robust optimization models,Manuja(2008)proposes a formulation for robust linear programming problems that allows the decision-maker to control both the probability and the expected value of constraint violation.Bandi and Bertsimas(2012)propose a new approach to analyze stochastic systems based on robust optimiza-tion.The key idea is to replace the Kolmogorov axioms and the concept of random variables as primitives of probability theory,with uncertainty sets that are derived from some of the asymptotic implications of probability theory like the central limit theorem.The authors show that the performance analysis questions become highly structured optimization problems for which there exist efficient algorithms that are capable of solving problems in high dimensions.They also demonstrate that the proposed approach achieves computationally tractable methods for(a)analyzing queueing networks,(b)designing multi-item,multi-bidder auctions with budget constraints,and (c)pricing multi-dimensional options.2.4.2Distributionally Robust OptimizationBen-Tal et al.(2010)considers the optimization of a worst-case expected-value criterion,where the worst case is computed over all probability distributions within a set.The contribution of the work is to define a notion of robustness that allows for different guarantees for different subsets of probability measures.The concept of distributional robustness is also explored in Goh and Sim(2010),with an emphasis on linear and piecewise-linear decision rules to reformulate the original problem in aflexible manner using expected-value terms.Xu et al.(2012) also investigates probabilistic interpretations of robust optimization.A related area of study is worst-case optimization with partial information on the moments of distributions.In particular,Popescu(2007)analyzes robust solutions to a certain class of stochastic optimization problems,using mean-covariance information about the distributions underlying the uncertain parameters.The author connects the problem for a broad class of objective functions to a univariate mean-variance robust objective and,subsequently, to a(deterministic)parametric quadratic programming problem.The reader is referred to Doan(2010)for a moment-based uncertainty model for stochastic optimization prob-lems,which addresses the ambiguity of probability distributions of random parameters with a minimax decision rule,and a comparison with data-driven approaches.Distributionally robust optimization in the context of data-driven problems is the focus of Delage(2009),which uses observed data to define a”well structured”set of dis-tributions that is guaranteed with high probability to contain the distribution from which the samples were drawn. Zymler et al.(2012a)develop tractable semidefinite programming(SDP)based approximations for distributionally robust individual and joint chance constraints,assuming that only thefirst-and second-order moments as well as the support of the uncertain parameters are given.Becker(2011)studies the distributionally robust optimization problem with known mean,covariance and support and develops a decomposition method for this family of prob-lems which recursively derives sub-policies along projected dimensions of uncertainty while providing a sequence of bounds on the value of the derived policy.Robust linear optimization using distributional information is further studied in Kang(2008).Further,Delage and Ye(2010)investigates distributional robustness with moment uncertainty.Specifically,uncertainty affects the problem both in terms of the distribution and of its moments.The authors show that the resulting problems can be solved efficiently and prove that the solutions exhibit,with high probability,best worst-case performance over a set of distributions.Bertsimas et al.(2010)proposes a semidefinite optimization model to address minimax two-stage stochastic linear problems with risk aversion,when the distribution of the second-stage random variables belongs to a set of multivariate distributions with knownfirst and second moments.The minimax solutions provide a natural distribu-tion to stress-test stochastic optimization problems under distributional ambiguity.Cromvik and Patriksson(2010a) show that,under certain assumptions,global optima and stationary solutions of stochastic mathematical programs with equilibrium constraints are robust with respect to changes in the underlying probability distribution.Works such as Zhu and Fukushima(2009)and Zymler(2010)also study distributional robustness in the context of specific applications,such as portfolio management.2.5Connection with Risk TheoryBertsimas and Brown(2009)describe how to connect uncertainty sets in robust linear optimization to coherent risk measures,an example of which is Conditional Value-at-Risk.In particular,the authors show the link between polyhedral uncertainty sets of a special structure and a subclass of coherent risk measures called distortion risk measures.Independently,Chen et al.(2007)present an approach for constructing uncertainty sets for robust opti-mization using new deviation measures that capture the asymmetry of the distributions.These deviation measures lead to improved approximations of chance constraints.Dentcheva and Ruszczynski(2010)proposes the concept of robust stochastic dominance and shows its applica-tion to risk-averse optimization.They consider stochastic optimization problems where risk-aversion is expressed by a robust stochastic dominance constraint and develop necessary and sufficient conditions of optimality for such optimization problems in the convex case.In the nonconvex case,they derive necessary conditions of optimality under additional smoothness assumptions of some mappings involved in the problem.2.6Nonlinear OptimizationRobust nonlinear optimization remains much less widely studied to date than its linear counterpart.Bertsimas et al.(2010c)presents a robust optimization approach for unconstrained non-convex problems and problems based on simulations.Such problems arise for instance in the partial differential equations literature and in engineering applications such as nanophotonic design.An appealing feature of the approach is that it does not assume any specific structure for the problem.The case of robust nonlinear optimization with constraints is investigated in Bertsimas et al.(2010b)with an application to radiation therapy for cancer treatment.Bertsimas and Nohadani (2010)further explore robust nonconvex optimization in contexts where solutions are not known explicitly,e.g., have to be found using simulation.They present a robust simulated annealing algorithm that improves performance and robustness of the solution.Further,Boni et al.(2008)analyzes problems with uncertain conic quadratic constraints,formulating an approx-imate robust counterpart,and Zhang(2007)provide formulations to nonlinear programming problems that are valid in the neighborhood of the nominal parameters and robust to thefirst order.Hsiung et al.(2008)present tractable approximations to robust geometric programming,by using piecewise-linear convex approximations of each non-linear constraint.Geometric programming is also investigated in Shen et al.(2008),where the robustness is injected at the level of the algorithm and seeks to avoid obtaining infeasible solutions because of the approximations used in the traditional approach.Interval uncertainty-based robust optimization for convex and non-convex quadratic programs are considered in Li et al.(2011).Takeda et al.(2010)studies robustness for uncertain convex quadratic programming problems with ellipsoidal uncertainties and proposes a relaxation technique based on random sampling for robust deviation optimization sserre(2011)considers minimax and robust models of polynomial optimization.A special case of nonlinear problems that are linear in the decision variables but convex in the uncertainty when the worst-case objective is to be maximized is investigated in Kawas and Thiele(2011a).In that setting,exact and tractable robust counterparts can be derived.A special class of nonconvex robust optimization is examined in Kawas and Thiele(2011b).Robust nonconvex optimization is examined in detail in Teo(2007),which presents a method that is applicable to arbitrary objective functions by iteratively moving along descent directions and terminates at a robust local minimum.3Applications of Robust OptimizationWe describe below examples to which robust optimization has been applied.While an appealing feature of robust optimization is that it leads to models that can be solved using off-the-shelf software,it is worth pointing the existence of algebraic modeling tools that facilitate the formulation and subsequent analysis of robust optimization problems on the computer(Goh and Sim,2011).3.1Production,Inventory and Logistics3.1.1Classical logistics problemsThe capacitated vehicle routing problem with demand uncertainty is studied in Sungur et al.(2008),with a more extensive treatment in Sungur(2007),and the robust traveling salesman problem with interval data in Montemanni et al.(2007).Remli and Rekik(2012)considers the problem of combinatorial auctions in transportation services when shipment volumes are uncertain and proposes a two-stage robust formulation solved using a constraint gener-ation algorithm.Zhang(2011)investigates two-stage minimax regret robust uncapacitated lot-sizing problems with demand uncertainty,in particular showing that it is polynomially solvable under the interval uncertain demand set.3.1.2SchedulingGoren and Sabuncuoglu(2008)analyzes robustness and stability measures for scheduling in a single-machine environment subject to machine breakdowns and embeds them in a tabu-search-based scheduling algorithm.Mittal (2011)investigates efficient algorithms that give optimal or near-optimal solutions for problems with non-linear objective functions,with a focus on robust scheduling and service operations.Examples considered include parallel machine scheduling problems with the makespan objective,appointment scheduling and assortment optimization problems with logit choice models.Hazir et al.(2010)considers robust scheduling and robustness measures for the discrete time/cost trade-off problem.3.1.3Facility locationAn important question in logistics is not only how to operate a system most efficiently but also how to design it. Baron et al.(2011)applies robust optimization to the problem of locating facilities in a network facing uncertain demand over multiple periods.They consider a multi-periodfixed-charge network location problem for which they find the number of facilities,their location and capacities,the production in each period,and allocation of demand to facilities.The authors show that different models of uncertainty lead to very different solution network topologies, with the model with box uncertainty set opening fewer,larger facilities.?investigate a robust version of the location transportation problem with an uncertain demand using a2-stage formulation.The resulting robust formulation is a convex(nonlinear)program,and the authors apply a cutting plane algorithm to solve the problem exactly.Atamt¨u rk and Zhang(2007)study the networkflow and design problem under uncertainty from a complexity standpoint,with applications to lot-sizing and location-transportation problems,while Bardossy(2011)presents a dual-based local search approach for deterministic,stochastic,and robust variants of the connected facility location problem.The robust capacity expansion problem of networkflows is investigated in Ordonez and Zhao(2007),which provides tractable reformulations under a broad set of assumptions.Mudchanatongsuk et al.(2008)analyze the network design problem under transportation cost and demand uncertainty.They present a tractable approximation when each commodity only has a single origin and destination,and an efficient column generation for networks with path constraints.Atamt¨u rk and Zhang(2007)provides complexity results for the two-stage networkflow anddesign plexity results for the robust networkflow and network design problem are also provided in Minoux(2009)and Minoux(2010).The problem of designing an uncapacitated network in the presence of link failures and a competing mode is investigated in Laporte et al.(2010)in a railway application using a game theoretic perspective.Torres Soto(2009)also takes a comprehensive view of the facility location problem by determining not only the optimal location but also the optimal time for establishing capacitated facilities when demand and cost parameters are time varying.The models are solved using Benders’decomposition or heuristics such as local search and simulated annealing.In addition,the robust networkflow problem is also analyzed in Boyko(2010),which proposes a stochastic formulation of minimum costflow problem aimed atfinding network design andflow assignments subject to uncertain factors,such as network component disruptions/failures when the risk measure is Conditional Value at Risk.Nagurney and Qiang(2009)suggests a relative total cost index for the evaluation of transportation network robustness in the presence of degradable links and alternative travel behavior.Further,the problem of locating a competitive facility in the plane is studied in Blanquero et al.(2011)with a robustness criterion.Supply chain design problems are also studied in Pan and Nagi(2010)and Poojari et al.(2008).3.1.4Inventory managementThe topic of robust multi-stage inventory management has been investigated in detail in Bienstock and Ozbay (2008)through the computation of robust basestock levels and Ben-Tal et al.(2009)through an extension of the Affinely Adjustable Robust Counterpart framework to control inventories under demand uncertainty.See and Sim (2010)studies a multi-period inventory control problem under ambiguous demand for which only mean,support and some measures of deviations are known,using a factor-based model.The parameters of the replenishment policies are obtained using a second-order conic programming problem.Song(2010)considers stochastic inventory control in robust supply chain systems.The work proposes an inte-grated approach that combines in a single step datafitting and inventory optimization–using histograms directly as the inputs for the optimization model–for the single-item multi-period periodic-review stochastic lot-sizing problem.Operation and planning issues for dynamic supply chain and transportation networks in uncertain envi-ronments are considered in Chung(2010),with examples drawn from emergency logistics planning,network design and congestion pricing problems.3.1.5Industry-specific applicationsAng et al.(2012)proposes a robust storage assignment approach in unit-load warehouses facing variable supply and uncertain demand in a multi-period setting.The authors assume a factor-based demand model and minimize the worst-case expected total travel in the warehouse with distributional ambiguity of demand.A related problem is considered in Werners and Wuelfing(2010),which optimizes internal transports at a parcel sorting center.Galli(2011)describes the models and algorithms that arise from implementing recoverable robust optimization to train platforming and rolling stock planning,where the concept of recoverable robustness has been defined in。
酒店管理理论 经济型酒店起源

酒店管理理论经济型酒店起源经济型酒店的发展和投资风险分析国外经济型酒店的发展分析国外经济型酒店的发展历程经济型酒店起源于美国,1951 年,凯蒙·威尔逊看准了汽车旅馆蕴藏的巨大商机,在通向田纳西州首府的孟菲斯城的主要通道上兴建了一座名为“HolidayInn”的拥有120 间客房的汽车旅馆,由于生意红火,他很快就开了连锁店。
与此同时,美国和欧洲的酒店集团也纷纷成立,其中多数的酒店集团是从经济型酒店起家的,如Best Western、Ramada 等等。
至二十世纪六、七十年代,随着美国在全国范围内大规模修建高速公路经济型酒店投资达到高潮。
美国经济型酒店在高速发展的同时,十分注重市场细分,大中城市多修建商务型的经济型酒店、旅游胜地多修建度假型的经济型酒店。
目前,美国经济型酒店有近140 个品牌,并有明确的市场定位,如,商务、观光、家庭等,且在硬件设施和服务配套等方面体现出不同的特色。
欧洲的经济型酒店情况相似,法国雅高集团旗下就有多个经济型酒店品牌,其中,Ibis 定位于商务型,Formula l 定位于个人旅游。
仅Ibis 品牌旗下的经济型酒店数量就达到700 多家。
由于银行金融业的渗入,许多区域性的经济型酒店集团已逐渐发展成世界性的酒店集团,引领着世界饭店业的发展。
经济型酒店在全球的发展经历了四个历史阶段:萌芽与发展初期;蓬勃发展时期;品牌调整时期;全球布局期。
(一)20 世纪30 年代末~50 年代末——萌芽与发展初期20 世纪30 年代后,随着美国大众消费的兴起,以及公路网络的发展,汽车旅馆开始出现,为平民的出游提供廉价的住宿服务。
二战后,美国经济的繁荣促生了大众旅游的兴起,引发了人们对中低档住宿设施的大量需求;城际高速公路网络的发展则促进了汽车旅馆的风行。
如1952 年诞生的假日汽车旅馆,它吸取了过去汽车旅馆发展的经验,重视改善服务质量,第一次尝试用标准化的方式复制其产品和服务,在短短的10 年时间里,沿着美国的公路网络迅速发展起来。
SOCIAL CAPITAL Its Origins and Applications in Modern Sociology

Annu.Rev.Sociol.1998.24:1–24Copyright ©1998by Annual Reviews.All rights reservedSOCIAL CAPITAL:Its Origins andApplications in Modern Sociology Alejandro Portes Department of Sociology,Princeton University,Princeton,New Jersey 08540KEY WORDS:social control,family support,networks,sociabilityA BSTRACTThispaper reviews the origins and definitionsof social capital in the writings of Bourdieu,Loury,and Coleman,among other authors.It distinguishes foursources of social capital and examines their dynamics.Applications of the concept in the sociological literature emphasize its role in social control,infamilysupport,and in benefits mediated by extrafamilial networks.I provideexamples of each of these positive functions.Negative consequences of thesame processes also deserve attention for a balanced picture of the forces at play.I review four such consequences and illustrate them with relevant ex-amples.Recent writings on social capital have extended the concept from an individual asset to a feature of communities and even nations.The final sec-tionsdescribe this conceptual stretch and examine its limitations.I argue that,as shorthand for the positive consequences of sociability,social capitalhas a definite place in sociological theory.However,excessive extensions of the concept may jeopardize its heuristic value.Alejandro Portes:Biographical SketchAlejandroPortes is professor of sociology at Princeton University andfaculty associate of the Woodrow Wilson School of Public Affairs.He for-merly taught at Johns Hopkins where he held the John Dewey Chair in Artsand Sciences,Duke University,and the University of Texas-Austin.In 1997he heldthe Emilio Bacardi distinguished professorship at the University ofMiami.In the same year he was elected president of the American Sociologi-cal Association.Born in Havana,Cuba,he came to the United States in 1960.He was educated at the University of Havana,Catholic University of Argen-tina,and Creighton University.He received his MA and PhD from the Uni-versity of Wisconsin-Madison.0360-0572/98/0815-0001$08.001A n n u . R e v . S o c i o l . 1998.24:1-24. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b yS w i ssAca dem icLi bra ryC onsor t iaon3/24/9.F orpe rsonaluseo nl y.Portes is the author of some 200articles and chapters on national devel-opment,international migration,Latin American and Caribbean urbaniza-tion,and economic sociology.His most recent books include City on the Edge,the Transformation of Miami (winner of the Robert Park award for best book in urban sociology and of the Anthony Leeds award for best book in urban anthropology in 1995);The New Second Generation (Russell Sage Foundation 1996);Caribbean Cities (Johns Hopkins University Press);and Immigrant America,a Portrait.The latter book was designated as a centen-nial publication by the University of California Press.It was originally pub-lished in 1990;the second edition,updated and containing new chapters on American immigration policy and the new second generation,was published in 1996.Introduction During recent years,the concept of social capital has become one of the most popular exports from sociological theory into everyday language.Dissemi-nated by a number of policy-oriented journals and general circulation maga-zines,social capital has evolved into something of a cure-all for the maladies affecting society at home and abroad.Like other sociological concepts that have traveled a similar path,the original meaning of the term and its heuristic value are being put to severe tests by these increasingly diverse applications.As in the case of those earlier concepts,the point is approaching at which so-cial capital comes to be applied to so many events and in so many different contexts as to lose any distinct meaning.Despite its current popularity,the term does not embody any idea really new to sociologists.That involvement and participation in groups can have positive consequences for the individual and the community is a staple notion,dating back to Durkheim’s emphasis on group life as an antidote to anomie and self-destruction and to Marx’s distinction between an atomized class-in-itself and a mobilized and effective class-for-itself.In this sense,the term social capital simply recaptures an insight present since the very beginnings of the disci-pline.Tracing the intellectual background of the concept into classical times would be tantamount to revisiting sociology’s major nineteenth century sources.That exercise would not reveal,however,why this idea has caught on in recent years or why an unusual baggage of policy implications has been heaped on it.The novelty and heuristic power of social capital come from two sources.First,the concept focuses attention on the positive consequences of sociability while putting aside its less attractive features.Second,it places those positive consequences in the framework of a broader discussion of capital and calls atten-tion to how such nonmonetary forms can be important sources of power and in-fluence,like the size of one’s stock holdings or bank account.The potential fungi-bility of diverse sources of capital reduces the distance between the sociologi-2PORTESA n n u . 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F o r p e r s o n a l u s e o n l y .cal and economic perspectives and simultaneously engages the attention of policy-makers seeking less costly,non-economic solutions to social problems.In the course of this review,I limit discussion to the contemporary reemer-gence of the idea to avoid a lengthy excursus into its classical predecessors.To an audience of sociologists,these sources and the parallels between present so-cial capital discussions and passages in the classical literature will be obvious.I examine,first,the principal authors associated with the contemporary usage of the term and their different approaches to it.Then I review the various mechanisms leading to the emergence of social capital and its principal appli-cations in the research literature.Next,I examine those not-so-desirable con-sequences of sociability that are commonly obscured in the contemporary lit-erature on the topic.This discussion aims at providing some balance to the fre-quently celebratory tone with which the concept is surrounded.That tone is es-pecially noticeable in those studies that have stretched the concept from a property of individuals and families to a feature of communities,cities,and even nations.The attention garnered by applications of social capital at this broader level also requires some discussion,particularly in light of the poten-tial pitfalls of that conceptual stretch.Definitions The first systematic contemporary analysis of social capital was produced by Pierre Bourdieu,who defined the concept as “the aggregate of the actual or po-tential resources which are linked to possession of a durable network of more or less institutionalized relationships of mutual acquaintance or recognition”(Bourdieu 1985,p.248;1980).This initial treatment of the concept appeared in some brief “Provisional Notes”published in the Actes de la Recherche en Sciences Sociales in 1980.Because they were in French,the article did not gar-ner widespread attention in the English-speaking world;nor,for that matter,did the first English translation,concealed in the pages of a text on the sociol-ogy of education (Bourdieu 1985).This lack of visibility is lamentable because Bourdieu’s analysis is arguably the most theoretically refined among those that introduced the term in contem-porary sociological discourse.His treatment of the concept is instrumental,fo-cusing on the benefits accruing to individuals by virtue of participation in groups and on the deliberate construction of sociability for the purpose of cre-ating this resource.In the original version,he went as far as asserting that “the profits which accrue from membership in a group are the basis of the solidarity which makes them possible”(Bourdieu 1985,p.249).Social networks are not a natural given and must be constructed through investment strategies oriented to the institutionalization of group relations,usable as a reliable source of other benefits.Bourdieu’s definition makes clear that social capital is decomposable into two elements:first,the social relationship itself that allows individuals to SOCIAL CAPITAL:ORIGINS AND APPLICATIONS 3A n n u . 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F o r p e r s o n a l u s e o n l y .claim access to resources possessed by their associates,and second,the amount and quality of those resources.Throughout,Bourdieu’s emphasis is on the fungibility of different forms of capital and on the ultimate reduction of all forms to economic capital,defined as accumulated human labor.Hence,through social capital,actors can gain di-rect access to economic resources (subsidized loans,investment tips,protected markets);they can increase their cultural capital through contacts with experts or individuals of refinement (i.e.embodied cultural capital);or,alternatively,they can affiliate with institutions that confer valued credentials (i.e.institu-tionalized cultural capital).On the other hand,the acquisition of social capital requires deliberate invest-ment of both economic and cultural resources.Though Bourdieu insists that the outcomes of possession of social or cultural capital are reducible to economic capital,the processes that bring about these alternative forms are not.They each possess their own dynamics,and,relative to economic exchange,they are characterized by less transparency and more uncertainty.For example,trans-actions involving social capital tend to be characterized by unspecified obliga-tions,uncertain time horizons,and the possible violation of reciprocity expec-tations.But,by their very lack of clarity,these transactions can help disguise what otherwise would be plain market exchanges (Bourdieu 1979,1980).A second contemporary source is the work of economist Glen Loury (1977,1981).He came upon the term in the context of his critique of neoclassical theories of racial income inequality and their policy implications.Loury ar-gued that orthodox economic theories were too individualistic,focusing exclu-sively on individual human capital and on the creation of a level field for com-petition based on such skills.By themselves,legal prohibitions against em-ployers’racial tastes and implementation of equal opportunity programs would not reduce racial inequalities.The latter could go on forever,according to Loury,for two reasons—first,the inherited poverty of black parents,which would be transmitted to their children in the form of lower material resources and educational opportunities;second,the poorer connections of young black workers to the labor market and their lack of information about opportunities:The merit notion that,in a free society,each individual will rise to the level justified by his or her competence conflicts with the observation that no one travels that road entirely alone.The social context within which individual maturation occurs strongly conditions what otherwise equally competent in-dividuals can achieve.This implies that absolute equality of opportunity,…is an ideal that cannot be achieved.(Loury 1977,p.176)Loury cited with approval the sociological literature on intergenerational mobility and inheritance of race as illustrating his anti-individualist argument.However,he did not go on to develop the concept of social capital in any detail.4PORTESA n n u . 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F o r p e r s o n a l u s e o n l y .He seems to have run across the idea in the context of his polemic against or-thodox labor economics,but he mentions it only once in his original article and then in rather tentative terms (Loury 1977).The concept captured the differen-tial access to opportunities through social connections for minority and nonmi-nority youth,but we do not find here any systematic treatment of its relations to other forms of capital.Loury’s work paved the way,however,for Coleman’s more refined analy-sis of the same process,namely the role of social capital in the creation of hu-man capital.In his initial analysis of the concept,Coleman acknowledges Loury’s contribution as well as those of economist Ben-Porath and sociolo-gists Nan Lin and Mark Granovetter.Curiously,Coleman does not mention Bourdieu,although his analysis of the possible uses of social capital for the ac-quisition of educational credentials closely parallels that pioneered by the French sociologist.1Coleman defined social capital by its function as “a vari-ety of entities with two elements in common:They all consist of some aspect of social structures,and they facilitate certain action of actors—whether per-sons or corporate actors—within the structure”(Coleman 1988a:p.S98,1990,p.302).This rather vague definition opened the way for relabeling a number of dif-ferent and even contradictory processes as social capital.Coleman himself started that proliferation by including under the term some of the mechanisms that generated social capital (such as reciprocity expectations and group en-forcement of norms);the consequences of its possession (such as privileged access to information);and the “appropriable”social organization that pro-vided the context for both sources and effects to materialize.Resources ob-tained through social capital have,from the point of view of the recipient,the character of a gift.Thus,it is important to distinguish the resources themselves from the ability to obtain them by virtue of membership in different social structures,a distinction explicit in Bourdieu but obscured in Coleman.Equat-ing social capital with the resources acquired through it can easily lead to tau-tological statements.2Equally important is the distinction between the motivations of recipients and of donors in exchanges mediated by social capital.Recipients’desire toSOCIAL CAPITAL:ORIGINS AND APPLICATIONS 51The closest equivalent to human capital in Bourdieu’s analysis is embodied cultural capital,which is defined as the habitus of cultural practices,knowledge,and demeanors learned through exposure to role models in the family and other environments (Bourdieu 1979).2Saying,for example,that student A has social capital because he obtained access to a large tuition loan from his kin and that student B does not because she failed to do so neglects the possibility that B’s kin network is equally or more motivated to come to her aid but simply lacks the means to do.Defining social capital as equivalent with the resources thus obtained is tantamount to saying that the successful succeed.This circularity is more evident in applications of social capital that define it as a property of collectivities.These are reviewed below.A n n u . R e v . S o c i o l . 1998.24:1-24. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y S w i s s A c a d e m i c L i b r a r y C o n s o r t i a o n 03/24/09. F o r p e r s o n a l u s e o n l y .gain access to valuable assets is readily understandable.More complex are the motivations of the donors,who are requested to make these assets available without any immediate return.Such motivations are plural and deserve analy-sis because they are the core processes that the concept of social capital seeks to capture.Thus,a systematic treatment of the concept must distinguish among:(a )the possessors of social capital (those making claims);(b )the sources of social capital (those agreeing to these demands);(c )the resources themselves.These three elements are often mixed in discussions of the concept following Coleman,thus setting the stage for confusion in the uses and scope of the term.Despite these limitations,Coleman’s essays have the undeniable merit of introducing and giving visibility to the concept in American sociology,high-lighting its importance for the acquisition of human capital,and identifying some of the mechanisms through which it is generated.In this last respect,his discussion of closure is particularly enlightening.Closure means the existence of sufficient ties between a certain number of people to guarantee the obser-vance of norms.For example,the possibility of malfeasance within the tightly knit community of Jewish diamond traders in New York City is minimized by the dense ties among its members and the ready threat of ostracism against vio-lators.The existence of such a strong norm is then appropriable by all members of the community,facilitating transactions without recourse to cumbersome legal contracts (Coleman 1988a:S99).After Bourdieu,Loury,and Coleman,a number of theoretical analyses of social capital have been published.In 1990,WE Baker defined the concept as “a resource that actors derive from specific social structures and then use to pursue their interests;it is created by changes in the relationship among actors”(Baker 1990,p.619).More broadly,M Schiff defines the term as “the set of elements of the social structure that affects relations among people and are in-puts or arguments of the production and/or utility function”(Schiff 1992,p.161).Burt sees it as “friends,colleagues,and more general contacts through whom you receive opportunities to use your financial and human capital”(Burt 1992,p.9).Whereas Coleman and Loury had emphasized dense net-works as a necessary condition for the emergence of social capital,Burt high-lights the opposite situation.In his view,it is the relative absence of ties,la-beled “structural holes,”that facilitates individual mobility.This is so because dense networks tend to convey redundant information,while weaker ties can be sources of new knowledge and resources.Despite these differences,the consensus is growing in the literature that so-cial capital stands for the ability of actors to secure benefits by virtue of mem-bership in social networks or other social structures.This is the sense in which it has been more commonly applied in the empirical literature although,as we will see,the potential uses to which it is put vary greatly.6PORTESA n n u . 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F o r p e r s o n a l u s e o n l y .Sources of Social CapitalBoth Bourdieu and Coleman emphasize the intangible character of social capital relative to other forms.Whereas economic capital is in people’s bank accounts and human capital is inside their heads,social capital inheres in the structure of their relationships.To possess social capital,a person must be related to others,and it is those others,not himself,who are the actual source of his or her advan-tage.As mentioned before,the motivation of others to make resources avail-able on concessionary terms is not uniform.At the broadest level,one may dis-tinguish between consummatory versus instrumental motivations to do so.As examples of the first,people may pay their debts in time,give alms to charity,and obey traffic rules because they feel an obligation to behave in this manner.The internalized norms that make such behaviors possible are then ap-propriable by others as a resource.In this instance,the holders of social capital are other members of the community who can extend loans without fear of nonpayment,benefit from private charity,or send their kids to play in the street without concern.Coleman (1988a:S104)refers to this source in his analysis of norms and sanctions:“Effective norms that inhibit crime make it possible to walk freely outside at night in a city and enable old persons to leave their houses without fear for their safety.”As is well known,an excessive emphasis on this process of norm internalization led to the oversocialized conception of human action in sociology so trenchantly criticized by Wrong (1961).An approach closer to the undersocialized view of human nature in modern economics sees social capital as primarily the accumulation of obligations from others according to the norm of reciprocity.In this version,donors pro-vide privileged access to resources in the expectation that they will be fully re-paid in the future.This accumulation of social chits differs from purely eco-nomic exchange in two aspects.First,the currency with which obligations are repaid may be different from that with which they were incurred in the first place and may be as intangible as the granting of approval or allegiance.Sec-ond,the timing of the repayment is unspecified.Indeed,if a schedule of repay-ments exists,the transaction is more appropriately defined as market exchange than as one mediated by social capital.This instrumental treatment of the term is quite familiar in sociology,dating back to the classical analysis of social ex-change by Simmel ([1902a]1964),the more recent ones by Homans (1961)and Blau (1964),and extensive work on the sources and dynamics of reciproc-ity by authors of the rational action school (Schiff 1992,Coleman 1994).Two other sources of social capital exist that fit the consummatory versus instrumental dichotomy,but in a different way.The first finds its theoretical underpinnings in Marx’s analysis of emergent class consciousness in the in-dustrial proletariat.By being thrown together in a common situation,workers learn to identify with each other and support each other’s initiatives.This soli-SOCIAL CAPITAL:ORIGINS AND APPLICATIONS 7A n n u . 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F o r p e r s o n a l u s e o n l y .darity is not the result of norm introjection during childhood,but is an emer-gent product of a common fate (Marx [1894]1967,Marx &Engels [1848]1947).For this reason,the altruistic dispositions of actors in these situations are not universal but are bounded by the limits of their community.Other members of the same community can then appropriate such dispositions and the actions that follow as their source of social capital.Bounded solidarity is the term used in the recent literature to refer to this mechanism.It is the source of social capital that leads wealthy members of a church to anonymously endow church schools and hospitals;members of a suppressed nationality to voluntarily join life-threatening military activities in its defense;and industrial proletarians to take part in protest marches or sym-pathy strikes in support of their fellows.Identification with one’s own group,sect,or community can be a powerful motivational force.Coleman refers to extreme forms of this mechanism as “zeal”and defines them as an effective an-tidote to free-riding by others in collective movements (Coleman 1990,pp.273–82;Portes &Sensenbrenner 1993).The final source of social capital finds its classical roots in Durkheim’s ([1893]1984)theory of social integration and the sanctioning capacity of group rituals.As in the case of reciprocity exchanges,the motivation of donors of socially mediated gifts is instrumental,but in this case,the expectation of re-payment is not based on knowledge of the recipient,but on the insertion of both actors in a common social structure.The embedding of a transaction into suchstructure has two consequences.First,the donor’s returns may come not8PORTESFigure 1Actual and potential gains and losses in transactions mediated by social capitalA n n u . 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F o r p e r s o n a l u s e o n l y .directly from the recipient but from the collectivity as a whole in the form of status,honor,or approval.Second,the collectivity itself acts as guarantor that whatever debts are incurred will be repaid.As an example of the first consequence,a member of an ethnic group may endow a scholarship for young co-ethnic students,thereby expecting not re-payment from recipients but rather approval and status in the collectivity.The students’social capital is not contingent on direct knowledge of their benefac-tor,but on membership in the same group.As an example of the second effect,a banker may extend a loan without collateral to a member of the same relig-ious community in full expectation of repayment because of the threat of com-munity sanctions and ostracism.In other words,trust exists in this situation precisely because obligations are enforceable,not through recourse to law or violence but through the power of the community.In practice,these two effects of enforceable trust are commonly mixed,as when someone extends a favor to a fellow member in expectation of both guaranteed repayment and group approval.As a source of social capital,en-forceable trust is hence appropriable by both donors and recipients:For recipi-ents,it obviously facilitates access to resources;for donors,it yields approval and expedites transactions because it ensures against malfeasance.No lawyer need apply for business transactions underwritten by this source of social capi-tal.The left side of Figure 1summarizes the discussion in this section.Keeping these distinctions in mind is important to avoid confusing consummatory and instrumental motivations or mixing simple dyadic exchanges with those em-bedded in larger social structures that guarantee their predictability and course.Effects of Social Capital:Recent Research Just as the sources of social capital are plural so are its consequences.The em-pirical literature includes applications of the concept as a predictor of,among others,school attrition and academic performance,children’s intellectual de-velopment,sources of employment and occupational attainment,juvenile de-linquency and its prevention,and immigrant and ethnic enterprise.3Diversity of effects goes beyond the broad set of specific dependent variables to which social capital has been applied to encompass,in addition,the character and meaning of the expected consequences.A review of the literature makes it pos-sible to distinguish three basic functions of social capital,applicable in a vari-ety of contexts:(a )as a source of social control;(b )as a source of family sup-port;(c )as a source of benefits through extrafamilial networks.SOCIAL CAPITAL:ORIGINS AND APPLICATIONS 93The following review does not aim at an exhaustive coverage of the empirical literature.That task has been rendered obsolete by the advent of computerized topical searches.My purpose instead is to document the principal types of application of the concept in the literature and to highlight their interrelationships.A n n u . R e v . S o c i o l . 1998.24:1-24. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y S w i s s A c a d e m i c L i b r a r y C o n s o r t i a o n 03/24/09. F o r p e r s o n a l u s e o n l y .As examples of the first function,we find a series of studies that focus on rule enforcement.The social capital created by tight community networks is useful to parents,teachers,and police authorities as they seek to maintain dis-cipline and promote compliance among those under their charge.Sources of this type of social capital are commonly found in bounded solidarity and en-forceable trust,and its main result is to render formal or overt controls unnec-essary.The process is exemplified by Zhou &Bankston’s study of the tightly knit Vietnamese community of New Orleans:Both parents and children are constantly observed as under a “Vietnamese microscope.”If a child flunks out or drops out of a school,or if a boy falls into a gang or a girl becomes pregnant without getting married,he or she brings shame not only to himself or herself but also to the family.(Zhou &Bankston 1996,p.207)The same function is apparent in Hagan et al’s (1995)analysis of right-wing extremism among East German beling right-wing extremism a sub-terranean tradition in German society,these authors seek to explain the rise of that ideology,commonly accompanied by anomic wealth aspirations among German adolescents.These tendencies are particularly strong among those from the formerly communist eastern states.That trend is explained as the joint outcome of the removal of social controls (low social capital),coupled with the long deprivations endured by East Germans.Incorporation into the West has brought about new uncertainties and the loosening of social integration,thus allowing German subterranean cultural traditions to re-emerge.Social control is also the focus of several earlier essays by Coleman,who laments the disappearance of those informal family and community structures that produced this type of social capital;Coleman calls for the creation of for-mal institutions to take their place.This was the thrust of Coleman’s 1992presidential address to the American Sociological Association,in which he traced the decline of “primordial”institutions based on the family and their re-placement by purposively constructed organizations.In his view,modern soci-ology’s task is to guide this process of social engineering that will substitute obsolete forms of control based on primordial ties with rationally devised ma-terial and status incentives (Coleman 1988b,1993).The function of social capital for social control is also evident whenever the concept is discussed in conjunction with the law (Smart 1993,Weede 1992).It is as well the central focus when it is defined as a property of collectivities such as cities or nations.This latter approach,associated mainly with the writings of political scientists,is discussed in a following section.The influence of Coleman’s writings is also clear in the second function of social capital,namely as a source of parental and kin support.Intact families and those where one parent has the primary task of rearing children possess 10PORTESA n n u . R e v . S o c i o l . 1998.24:1-24. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y S w i s s A c a d e m i c L i b r a r y C o n s o r t i a o n 03/24/09. F o r p e r s o n a l u s e o n l y .。
Evidence on the Trade-Off between Real Activities Manipulation and Accrual-Based Earnings Management

Evidence on the trade-off between real activities manipulation and accrual-based earningsmanagementAmy Y. ZangThe Hong Kong University of Science and TechnologyAbstract: I study whether managers use real activities manipulation and accrual-based earnings management as substitutes in managing earnings. I find that managers trade off the two earnings management methods based on their relative costs and that managers adjust the level of accrual-based earnings management according to the level of real activities manipulation realized. Using an empirical model that incorporates the costs associated with the two earnings management methods and captures managers’ sequential decisions, I document large sample evidence consistent with managers using real activities manipulation and accrual-based earnings management as substitutes.Keywords:real activities manipulation, accrual-based earnings management, trade-off Data Availability:Data are available from public sources indicated in the text.I am grateful for the guidance from my dissertation committee members, Jennifer Francis (chair), Qi Chen, Dhananjay Nanda, Per Olsson and Han Hong. I am also grateful for the suggestions and guidance received from Steven Kachelmeier (senior editor), Dan Dhaliwal and two anonymous reviewers. I thank Allen Huang, Moshe Bareket, Yvonne Lu, Shiva Rajgopal, Mohan Venkatachalam and Jerry Zimmerman for helpful comments. I appreciate the comments from the workshop participants at Duke University, University of Notre Dame, University of Utah, University of Arizona, University of Texas at Dallas, Dartmouth College, University of Oregon, Georgetown University, University of Rochester, Washington University in St. Louis and the HKUST. I gratefully acknowledge the financial support from the Fuqua School of Business at Duke University, the Deloitte Foundation, University of Rochester and the HKUST. Errors and omissions are my responsibility.I.INTRODUCTIONI study how firms trade off two earnings management strategies, real activities manipulation and accrual-based earnings management, using a large sample of firms over 1987–2008. Prior studies have shown evidence of firms altering real activities to manage earnings (e.g., Roychowdhury 2006; Graham et al. 2005) and evidence that firms make choices between the two earnings management strategies (Cohen et al. 2008; Cohen and Zarowin 2010; Badertscher 2011). My study extends research on the trade-off between real activities manipulation and accrual-based earnings management by documenting a set of variables that explain the costs of both real and accrual earnings management. I provide evidence for the trade-off decision as a function of the relative costs of the two activities and show that there is direct substitution between them after the fiscal year end due to their sequential nature.Real activities manipulation is a purposeful action to alter reported earnings in a particular direction, which is achieved by changing the timing or structuring of an operation, investment or financing transaction, and which has suboptimal business consequences. The idea that firms engage in real activities manipulation is supported by the survey evidence in Graham et al. (2005).1 They report that 80 percent of surveyed CFOs stated that, in order to deliver earnings, they would decrease research and development (R&D), advertising and maintenance expenditures, while 55 percent said they would postpone a new project, both of which are real activities manipulation.1 In particular, Graham et al. (2005) note that: “The opinion of many of the CFOs is that every companywould/should take actions such of these [real activities manipulation] to deliver earnings, as long as the real sacrifices are not too large and as long as the actions are within GAAP.” Graham et al. further conjecture that CFOs’ greater emphasis on real activities manipulation rather than accrual-based earnings management may be due to their reluctance to admit to accounting-based earnings management in the aftermath of the Enron and Worldcom accounting scandals.Unlike real activities manipulation, which alters the execution of a real transaction taking place during the fiscal year, accrual-based earnings management is achieved by changing the accounting methods or estimates used when presenting a given transaction in the financial statements. For example, changing the depreciation method for fixed assets and the estimate for provision for doubtful accounts can bias reported earnings in a particular direction without changing the underlying transactions.The focus of this study is on how managers trade off real activities manipulation and accrual-based earnings management. This question is important for two reasons. First, as mentioned by Fields et al. (2001), examining only one earnings management technique at a time cannot explain the overall effect of earnings management activities. In particular, if managers use real activities manipulation and accrual-based earnings management as substitutes for each other, examining either type of earnings management activities in isolation cannot lead to definitive conclusions. Second, by studying how managers trade off these two strategies, this study sheds light on the economic implications of accounting choices; that is, whether the costs that managers bear for manipulating accruals affect their decisions about real activities manipulation. As such, the question has implications about whether enhancing SEC scrutiny or reducing accounting flexibility in GAAP, for example, might increase the levels of real activities manipulation engaged in by firms.I start by analyzing the implications for managers’ trade-off decisions due to the different costs and timing of the two earnings management strategies. First, because both are costly activities, firms trade off real activities manipulation versus accrual-based earnings management based on their relative costliness. That is, when one activity is relatively more costly, firms engage in more of the other. Because firms face different costs and constraints for the twoearnings management approaches, they show differing abilities to use the two strategies. Second, real activities manipulation must occur during the fiscal year and is realized by the fiscal year end, after which managers still have the chance to adjust the level of accrual-based earnings management. This timing difference implies that managers would adjust the latter based on the outcome of real activities manipulation. Hence, there is also a direct, substitutive relation between the two: if real activities manipulation turns out to be unexpectedly high (low), managers will decrease (increase) the amount of accrual-based earnings management they carry out.Following prior studies, I examine real activities manipulation through overproduction and cutting discretionary expenditures (Roychowdhury 2006; Cohen et al. 2008; Cohen and Zarowin 2010). I test the hypotheses using a sample of firms that are likely to have managed earnings. As suggested by prior research, earnings management is likely to occur when firms just beat/meet an important earnings benchmark (Burgstahler and Dichev 1997; DeGeorge et al. 1999). Using a sample containing more than 6,500 earnings management suspect firm-years over the period 1987–2008, I show the empirical results that real activities manipulation is constrained by firms’ competitive status in the industry, financial health, scrutiny from institutional investors, and the immediate tax consequences of manipulation. The results also show that accrual-based earnings management is constrained by the presence of high-quality auditors; heightened scrutiny of accounting practice after the passage of the Sarbanes-Oxley Act (SOX); and firms’ accounting flexibility, as determined by their accounting choices in prior periods and the length of their operating cycles. I find significant positive relations between the level of real activities manipulation and the costs associated with accrual-based earnings management, and also between the level of accrual-based earnings management and the costs associated with realactivities manipulation, supporting the hypothesis that managers trade off the two approaches according to their relative costliness. There is a significant and negative relation between the level of accrual-based earnings management and the amount of unexpected real activities manipulation, consistent with the hypothesis that managers “fine-tune” accruals after the fiscal year end based on the realized real activities manipulation. Additional Hausman tests show results consistent with the decision of real activities manipulation preceding the decision of accrual-based earnings management.Two recent studies have examined the trade-off between real activities manipulation and accrual-based earnings management. Cohen et al. (2008) document that, after the passage of SOX, the level of accrual-based earnings management declines, while the level of real activities manipulation increases, consistent with firms switching from the former to the latter as a result of the post-SOX heightened scrutiny of accounting practice. Cohen and Zarowin (2010) show that firms engage in both forms of earnings management in the years of a seasoned equity offering (SEO). They show further that the tendency for SEO firms to use real activities manipulation is positively correlated with the costs of accrual-based earnings management in these firms.2 Compared to prior studies, this study contributes to the earnings management literature by providing a more complete picture of how managers trade off real activities manipulation and accrual-based earnings management. First, it documents the trade-off in a more general setting by using a sample of firms that are likely to have managed earnings to beat/meet various earnings targets. The evidence for the trade-off decisions discussed in this study does not depend on a specific period (such as around the passage of SOX, as in Cohen et al. 2008) or a significant corporate event (such as a SEO, as in Cohen and Zarowin 2010).2 Cohen and Zarowin (2010) do not examine how accrual-based earnings management for SEO firms varies based on the costs of real and accrual earnings management.Second, to my knowledge, mine is the first study to identify a set of costs for real activities manipulation and to examine their impact on both real and accrual earnings management activities. Prior studies (Cohen et al. 2008; Cohen and Zarowin 2010) only examine the costs of accrual-based earnings management. By including the costs of real activities manipulation, this study provides evidence for the trade-off as a function of the relative costs of the two approaches. That is, the level of each earnings management activity decreases with its own costs and increases with the costs of the other. In this way, I show that firms prefer different earnings management strategies in a predictive manner, depending on their operational and accounting environment.Third, I consider the sequential nature of the two earnings management strategies. Most prior studies on multiple accounting and/or economic choices implicitly assume that managers decide on multiple choices simultaneously without considering the sequential decision process as an alternative process (Beatty et al. 1995; Hunt et al. 1996; Gaver and Paterson 1999; Barton 2001; Pincus and Rajgopal 2002; Cohen et al. 2008; Cohen and Zarowin 2010). In contrast, my empirical model explicitly considers the implication of the difference in timing between the two earnings management approaches. Because real activities manipulation has to occur during the fiscal year, but accrual manipulation can occur after the fiscal year end, managers can adjust the extent of the latter based on the realized outcomes of the former. I show that, unlike the trade-off during the fiscal year, which is based on the relative costliness of the two strategies, there is a direct substitution between the two approaches at year end when real activities manipulation is realized. Unexpectedly high (low) real activities manipulation realized is directly offset by a lower (higher) amount of accrual earnings management.Section II reviews relevant prior studies. Section III develops the hypotheses. Section IV describes the research design, measurement of real activities manipulation, accrual-based earnings management and independent variables. Section V reports sample selection and empirical results. Section VI concludes and discusses the implications of my results.II.RELATED LITERATUREThe extensive literature on earnings management largely focuses on accrual-based earnings management (reviewed by Schipper 1989; Healy and Wahlen 1999; Fields et al. 2001). A smaller stream of literature investigates the possibility that managers manipulate real transactions to distort earnings. Many such studies examine managerial discretion over R&D expenditures (Baber et al. 1991; Dechow and Sloan 1991; Bushee 1998; Cheng 2004). Other types of real activities manipulation that have been explored include cutting advertising expenditures (Cohen et al. 2010), stock repurchases (Hribar et al. 2006), sales of profitable assets (Herrmann et al. 2003; Bartov 1993), sales price reductions (Jackson and Wilcox 2000), derivative hedging (Barton 2001; Pincus and Rajgopal 2002), debt-equity swaps (Hand 1989), and securitization (Dechow and Shakespeare 2009).The prevalence of real activities manipulation as an earnings management tool was not well understood until recent years. Graham et al. (2005) survey more than 400 executives and document the widespread use of real activities manipulation. Eighty percent of the CFOs in their survey stated that, in order to meet an earnings target, they would decrease expenditure on R&D, advertising and maintenance, while 55 percent said they would postpone a new project, even if such delay caused a small loss in firm value. Consistent with this survey, Roychowdhury (2006) documents large-sample evidence suggesting that managers avoid reporting annual losses ormissing analyst forecasts by manipulating sales, reducing discretionary expenditures, and overproducing inventory to decrease the cost of goods sold, all of which are deviations from otherwise optimal operational decisions, with the intention of biasing earnings upward.Recent research has started to examine the consequence of real activities manipulation. Gunny (2010) finds that firms that just meet earnings benchmarks by engaging in real activities manipulation have better operating performance in the subsequent three years than do firms that do not engage in real activities manipulation and miss or just meet earnings benchmarks. Bhojraj et al. (2009), on the other hand, show that firms that beat analyst forecasts by using real and accrual earnings management have worse operating performance and stock market performancein the subsequent three years than firms that miss analyst forecasts without earnings management.Most previous research on earnings management examines only one earnings management tool in settings where earnings management is likely to occur (e.g., Healy 1985; Dechow and Sloan 1991; Roychowdhury 2006). However, given the portfolio of earnings management strategies, managers probably use multiple techniques at the same time. A few prior studies (Beatty et al. 1995; Hunt et al. 1996; Gaver and Paterson 1999; Barton 2001; Pincus and Rajgopal 2002; Cohen et al. 2008; Cohen and Zarowin 2010; Badertscher 2011) examine how managers use multiple accounting and operating measures to achieve one or more goals.Beatty et al. (1995) study a sample of 148 commercial banks. They identify two accrual accounts (loan loss provisions and loan charge-offs) and three operating transactions (pension settlement transactions, miscellaneous gains and losses due to asset sales, and issuance of new securities) that these banks can adjust to achieve three goals (optimal primary capital, reported earnings and taxable income levels). The authors construct a simultaneous equation system, in which the banks minimize the sum of the deviations from the three goals and from the optimallevels of the five discretionary accounts.3 They find evidence that some, but not all, of the discretionary accounts (including both accounting choices and operating transactions) are adjusted jointly for some of the objectives identified.Barton (2001) and Pincus and Rajgopal (2002) study how firms manage earning volatility using a sample of Fortune 500, and oil and gas, firms respectively. Both studies use simultaneous equation systems, in which derivative hedging and accrual management are simultaneously determined to manage earnings volatility. Barton (2001) suggests that the two activities are used as substitutes, as evidenced by the negative relation between the two after controlling for the desired level of earnings volatility. Pincus and Rajgopal (2002) find similar negative relation, but only in the fourth quarter.There are two limitations in the approach taken by the above studies. First, in the empirical tests, they assume that the costs of adjusting discretionary accounts are constant across all firms and hence do not generate predictions or incorporate empirical proxies for the costs. In other words, they do not consider that discretion in some accounts is more costly to adjust for some firms. Hence, these studies fail to consider the trade-off among different tools due to their relative costs. Second, they assume all decisions are made simultaneously. If some decisions are made before others, this assumption can lead to misspecification in their equation system.Badertscher (2011) examines overvaluation as an incentive for earnings management. He finds that during the sustained period of overvaluation, managers use accrual earnings management in early years, real activities manipulation in later years, and non-GAAP earnings management as a last resort. He claims that the duration of overvaluation is an important determinant in managers’ choice of earnings management approaches, but he does not model the3Hunt et al. (1996) and Gaver and Paterson (1999) follow Beatty et al. (1995) and construct similar simultaneous equation systems.trade-off between real activities manipulation and accrual-based earnings management based on their relative costliness, nor does his study examine the implication of the sequential nature of the two activities during the year.Two recent studies examine the impact of the costs of accrual-based earnings management on the choice of earnings management strategies. Cohen et al. (2008) show that, on average, accrual-based earnings management declines, but real activities manipulation increases, after the passage of SOX. They focus on one cost of accrual-based earnings management, namely the heightened post-SOX scrutiny of accounting practice, and its impact on the levels of real and accrual earnings management. Using a sample of SEO firms, Cohen and Zarowin (2010) examine several costs of accrual-based earnings management and show that they are positively related to the tendency to use real activities manipulation in the year of a SEO. Neither study examines the costs of real activities manipulation or considers the sequential nature of the two strategies. Hence, they do not show the trade-off decision as a function of the relative costs of the two strategies or the direct substitution between the two after the fiscal year end.III.HYPOTHESES DEVELOPMENTConsistent with prior research on multiple earnings management strategies, I predict that managers use real activities manipulation and accrual-based earnings management as substitutes to achieve the desired earnings targets. Unlike prior research, however, I investigate the differences in the costs and timing of real activities manipulation and accrual-based earnings management, and their implications for managers’ trade-off decisions.Both real activities manipulation and accrual-based earnings management are costly activities. Firms are likely to face different levels of constraints for each strategy, which will leadto varying abilities to use them. A manager’s trade-off decision, therefore, depends on the relative costliness of the two earnings management methods, which is in turn determined by the firm’s operational and accounting environment. That is, given the desired level of earnings, when discretion is more constrained for one earnings management tool, the manager will make more use of the other. This expectation can be expressed as the following hypothesis: H1: Other things being equal, the relative degree of accrual-based earnings management vis-à-vis real activities manipulation depends on the relative costs of each action.Accrual-based earnings management is constrained by scrutiny from outsiders and the available accounting flexibility. For example, a manager might find it harder to convince a high-quality auditor of his/her aggressive accounting estimates than a low-quality auditor. A manager might also feel that accrual-based earnings management is more likely to be detected when regulators heighten scrutiny of firms’ accounting practice. Other than scrutiny from outsiders, accrual-based earnings management is constrained by the flexibility within firms’ accounting systems. Firms that are running out of such flexibility due to, for example, their having made aggressive accounting assumptions in the previous periods, face an increasingly high risk of being detected by auditors and violating GAAP with more accrual-based earnings management. Hence, I formulate the following two subsidiary hypotheses to H1:H1a: Other things being equal, firms facing greater scrutiny from auditors and regulators have a higher level of real activities manipulation.H1b: Other things being equal, firms with lower accounting flexibility have a higher level of real activities manipulation.Real activities manipulation, as a departure from optimal operational decisions, is unlikely to increase firms’ long-term value. Some managers might find it particularly costly because theirfirms face intense competition in the industry. Within an industry, firms are likely to face various levels of competition and, therefore, are under different amounts of pressure when deviating from optimal business strategies. Management research (as reviewed by Woo 1983) shows that market leaders enjoy more competitive advantages than do followers, due to their greater cumulative experience, ability to benefit from economies of scale, bargaining power with suppliers and customers, attention from investors, and influence on their competitors. Therefore, managers in market-leader firms may perceive real activities manipulation as less costly because the erosion to their competitive advantage is relatively small. Hence, I predict the following: H1c: Other things being equal, firms without market-leader status have a higher level of accrual-based earnings management.For a firm in poor financial health, the marginal cost of deviating from optimal business strategies is likely to be high. In this case, managers might perceive real activities manipulation as relatively costly because their primary goal is to improve operations. This view is supported by the survey evidence documented by Graham et al. (2005), who find that CFOs admit that if the company is in a “negative tailspin,” managers’ efforts to survive will dominate their reporting concerns. This reasoning leads to the following subsidiary hypothesis to H1: H1d: Other things being equal, firms with poor financial health have a higher level of accrual-based earnings management.Managers might find it difficult to manipulate real activities when their operation is being monitored closely by institutional investors. Prior studies suggest that institutional investors play a monitoring role in reducing real activities manipulation.4 Bushee (1998) finds that, when4 However, there is also evidence that “transient” institutions, or those with high portfolio turnover and highly diversified portfolio holdings, increase managerial myopic behavior (e.g., Porter 1992; Bushee 1998; Bushee 2001). In this study, I focus on the average effect of institutional ownership on firms’ earnings management activities without looking into the investment horizon of different institutions.institutional ownership is high, firms are less likely to cut R&D expenditure to avoid a decline in earnings. Roychowdhury (2006) also finds a negative relation between institutional ownership and real activities manipulation to avoid losses. Unlike accrual-based earnings management, real activities manipulation has real economic consequences for firms’ long-term value. Institutional investors, being more sophisticated and informed than other investors, are likely to have a better understanding of the long-term implication of firms’ operating decisions, leading to more effort to monitor and curtail real activities manipulation than accrual-based earnings management, as predicted in the following subsidiary hypothesis:H1e: Other things being equal, firms with higher institutional ownership have a higher level of accrual-based earnings management.Real activities manipulation is also costly due to tax incentives. It might be subject to a higher level of book-tax conformity than accrual-based earnings management, because the former has a direct cash flow effect in the current period, while the latter does not. Specifically, when firms increase book income by cutting discretionary expenditures or by overproducing inventory, they also increase taxable income and incur higher tax costs in the current period.5 In contrast, management of many accrual accounts increases book income without current-period tax consequences. For example, increasing the estimated useful lives of long-term assets, decreasing write-downs for impaired assets, recognizing unearned revenue aggressively, and decreasing bad debt expense can all increase book income without necessarily increasing current-year taxable income. Therefore, for firms with higher marginal tax rates, the net present value of the tax costs associated with real activities manipulation is likely to be higher than that of accrual-based earnings management, leading to the following prediction:5Other types of real activities manipulation, such as increasing sales by discounts and price cuts, and sale of long-term assets, are also book-tax conforming earnings management.H1f: Other things being equal, firms with higher marginal tax rates have a higher level of accrual-based earnings management.Another difference between the two earnings management strategies that will influence managers’ trade-off decisions is their different timing. H1 predicts that the two earnings management strategies are jointly determined and the trade-off depends on their relative costliness. However, a joint decision does not imply a simultaneous decision. Because real activities manipulation changes the timing and/or structuring of business transactions, such decisions and activities have to take place during the fiscal year. Shortly after the year end, the outcome of the real activities manipulation is revealed, and managers can no longer engage in it. Note that, when a manager alters real business decisions to manage earnings, s/he does not have perfect control over the exact amount of the real activities manipulation attained. For example, a pharmaceutical company cuts current-period R&D expenditure by postponing or cancelling development of a certain drug. This real decision can include a hiring freeze and shutting down the research site. The manager may be able to make a rough estimate of the dollar amount of the impact on R&D expenditure from these decisions, but s/he does not have perfect information about it.6 Therefore, managers face uncertainty when they execute real activities manipulation. After the fiscal year end, the realized amount of the real activities manipulation could be higher or lower than the amount originally anticipated.On the other hand, after the fiscal year end but before the earnings announcement date, managers can still adjust the accruals by changing the accounting estimates or methods. In addition, unlike real activities manipulation, which distorts earnings by executing transactions6 Another example is reducing travelling expenditures by requiring employees to fly economy class instead of allowing them to fly business class. This change could be suboptimal because employees might reduce the number of visit they make to important clients or because employees’ morale might be adversely impacted, leading to greater turnover. The manager cannot know for certain the exact amount of SG&A being cut, as s/he does not know the number of business trips taken by employees during the year.。
Hotelling模型
当 a=1-b 时,两个商店位于同一位置,我们走到另一个极端:
* * p1 (a,1 a) p2 (a,1 a) c
课后习题:P77 NO.7 (产品有差异时的价格竞争)现在假设两个企业的产品并不完全相同,企业 1 的需求函数为 q1 ( p1 , p2 ) a p1 p2 , 企业 2 的需求函数为 q2 ( p1 , p2 ) a p2 p1 。 求两个企业同时选择价格时的纳什均衡。
豪泰林(Hotelling)价格竞争模型 在古诺模型中 ,产品是同质的. 在这个假设下 ,如果企业的竞争战略是价格而 不是产量, 伯特兰德证明,即使只有两个企业 ,在均衡情况下 ,价格等于边际成本 , 企业的利润为零,与完全竞争市场均衡一样.这便是所谓的伯特兰德悖论. 解开这个悖论的办法之一是引入产品的差异性.如果不同企业生产的产品是 有差异的,替代弹性就不会是无限的,此时消费者对不同企业的产品有着不同的偏 好,价格不是他们感兴趣的唯一变量. 在存在产品差异的情况下,均衡价格不会等 于边际成本,垄断性提高. 产品差异有多种形式.我们现在考虑一种特殊的差异,即空间上的差异,这就是 经典的豪泰林模型 .在豪泰林模型中, 产品在物质性能上是相同的,但在空间位置 上有差异.因为不同位置上的消费者支付不同的运输成本,他们关心的是价格与运 输成本之和,而不单是价格.假定有一个长度为 1 的线性城市,消费者均匀地分布在 [0,1]区间里 ,分布密度为 1.假定有两个商店 , 分别位于城市的两端, 商店 1 在 x=0, 商店 2 在 x=1,出售物质性能相同的产品.每个商品提供单位产品的成本为 c,消费 者购买商品的旅行成本与离商店成比例,单位距离的成本为 t.这样,住在 x 的消费 者如果在商店 1 采购,要花费 tx 的旅行成本;如果在商店 2 采购,要花费 t(1-x).假定 消费者具有单位需求,即或者消费 1 个单位或者消费 0 个单位.消费者从消费中得 到的消费剩余为 s .
Hotelling-model以及两个扩展和多党竞选模型解析
基本思路: 假定两家厂商生产的同种产品具有质量差异, 及消费者对产品质量偏好服从 [d,e]
区间上的均匀分布,研究二次运输成本下两家厂商的选址和价格竞争的二阶段完全 信息动态博弈问题。 假设: (1)长度为1的“ 线性城市”; (2)交通费用为距离的二次函数,单位交通费用为t (3)消费者对产品质量的偏好 在 [d,e ]区间均匀分布,
w
x1 x2 m或x1 x2 m x1 = x2 = m
m x1 x2或m x1 x2
• 当x2 < m,党派1的最优策略x1为大于x2,小于2m-x2之间的任意数。 • 当x2 = m时,那么党派1的最优策略x1=x2。 • 当x2 > m,党派1的最优策略x1为大于2m-x2 ,小于x2之间的任意数。
1、来源:1838“伯特兰德悖论”———解决:引入产品差异性;特殊空间上的差异。 1929哈罗德·霍特林——经典Hotelling模型。
2、基本假设: (1)产品同质。 (2)决策变量:价格。 (3)成本函数相同,且AC=MC=C0; (4)长度为1的线性市场,两个厂商,消费者均匀分布,每个消费者购买一件商品。 (5)消费者购买商品的交通成本与离商店的距离成比例,单位距离的交通成本为t。
Hotelling模型中企业选址问题——转化成跨国企业选择经营何种品牌 产品的问题。
一、单一 A品牌经营下跨国公司的均衡利润 和基本模型 中 A、 B两企业 进行竞争的结果相同:
二、单一 D品牌经营下跨国公司的均衡利润 1、 先考虑给定 的情况下 ,B企业的两种选择 : 第一种, 在 [ x ,1 ] 区间 内达到利润最大化:
启示 1 跨国公司并购我国企业后,在大多数情况下并不会选择弃
用我国民族品牌,现有民族品牌被弃用的例子,可能是因为
基于Hotelling模型的双头竞争策略分析
华中科技大学硕士学位论文基于Hotelling模型的双头竞争策略分析姓名:魏贞申请学位级别:硕士专业:概率论与数理统计指导教师:杨明20061001华中科技大学硕士学位论文摘要双寡头竞争是市场竞争的主要形式,而且双寡头竞争已经包含了博弈论的主要内容,是博弈论早期研究的起点,也是博弈论在经济生活中的主要应用。
在现代经济竞争飞速的发展趋势下,企业的竞争策略研究面临改进和研究工具的更新,建立模型讨论新的策略效应和引进更好的评价工具不仅可以更好指导企业决策,也能更广泛地应用于实际。
本文在经典的竞争策略理论研究基础上,以博弈论、信息经济学、产业组织理论和实物期权方法为工具,集中深入地研究了基于Hotelling模型下的,可以根据顾客消费行为来进行价格歧视的企业定价策略和投资决策,并就不同的市场进行了分别的探讨。
本文的主要研究内容为:一、运用博弈论和产业组织理论知识分析了在能识别顾客并进行价格歧视的线性两期寡头市场中切换成本对公司均衡价格和对公司提供的折扣大小的影响,并简要讨论了公司理性与均衡价格的关系。
二、将两期模型扩展为公司生命无限期,顾客的生命期为两期的动态模型。
用博弈方法得出了两公司的均衡价格,并考察了作为状态变量的市场份额的动态演变过程和顾客的理性对公司的均衡价格的影响。
还分析了公司理性对于市场份额的收敛的作用。
三、将离散模型扩展成为连续时间模型,运用实物期权方法站在后进入公司的立场分别在市场是线性的和非线性的情况下评价了公司的投资决策。
并且通过图形描述了公司提供给新顾客的折扣对投资阈值的影响。
关键词:双寡头竞争;Hotelling模型;切换成本;均衡价格;折现因子华中科技大学硕士学位论文AbstractDuopoly competition, as the important form of market competition, contains the main contents of game theory. It is not only the jumping-off point of game theory but also the primary application. With the modern economic competition developing, the competition strategy needs amelioration and update as well as the research tools. The introduction of better approaches can help the corporation obtain preferable strategy. It can also be applied wider in practice.The paper, on the basis of the classical theory about competition strategy, concentrates on the pricing and investment strategy in different markets, in virtue of the game theory, information economics, industrial organization theory and real option approach.The main contents and conclusions are summarized as follows: First, company’s pricing strategy is studied in a two-period duopoly model with business practice of offering discounts to new customers in markets with switching costs, and equilibrium result shows how the existence of switching costs affects the price in both period. Then, such a situation is considered in which there is a duopoly with infinitely lived firms and overlapping generations of consumers where both firms can set different price for their previous customers and their new customers, and equilibrium results in two cases and the effect of the consumer patience on the price are analyzed. At the same time, the evolution trend of market shares affected by firm patience is obtained. Finally, Taking the place of discrete model into a continuous time one, the investment method in real option theory is applied to evaluate the new entrant’s strategy to invest respectively in linear market and non-linear one. Furthermore, the effect of the discount offered to new consumer on investment threshold has been displayed through figures.Key Words: duopoly competition; Hotelling model; switching costs; equilibrium price;discount factor独创性声明本人声明所呈交的学位论文是我个人在导师指导下进行的研究工作及取得的研究成果。
Dixit-Stiglitz1977垄断竞争模型工作论文
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Avinash K. Dixit and Joseph E. Stiglitz
and how much of each to produce, may differ. There are a number of effects at work. Whether a commodity is produced depends on revenues relative to total costs. Social profitability depends, on the other hand, on a number of factors. In deciding whether to produce a commodity, the government would look not only at the profitability of the project, but also at the consumer surplus (the profitability it could attain if it were acting as a completely discriminating monopolist), and the effect on other industries and sectors (on the consumer surplus, profitability and viability). The effects on other sectors result both from substitution and income effects. The whole problem hinges crucially on the existence of economies of scale. In their absence, it would be possible to produce infinitesimal amounts of every conceivable product that might be desired, without any additional resource cost. Private and social profitability would coincide given the other conventional assumptions, and the repercussions on other sectors would become purely pecuniary externalities. With nonconvexities, however, we shall see that all these considerations are altered. Moreover, given economies of scale in the relevant range of output, market realisation of the ‘unconstrained’ or first-best optimum, i.e. one subject to constraints of resource availability and technology alone, requires pricing below average cost, with lump-sum transfers to firms to cover losses. The conceptual and practical difficulties of doing so are clearly formidable. It would therefore appear that perhaps a more appropriate notion of optimality is a constrained one, where each firm must operate without making a loss. The government may pursue conventional regulatory policies, or combinations of excise and franchise taxes and subsidies, but the important restriction is that lump-sum subsidies are not possible. The permissible output and price configurations in such an optimum reflect the same constraints as the ones in the Chamberlinian equilibrium. The two solutions can still differ because of differences implicit in the objective functions. Consider first the manner in which the desirability of variety can enter into the model. Some such notion is already implicit in the convexity of indifference surfaces of a conventional utility function defined over quantities of all the varieties that might exist. Thus, a person who might be indifferent between the combinations of quantities (1, 0) and (0, 1) of two product types would prefer the combination ( 1 , 1 ) to either extreme. 2 2 If this is the only relevant consideration, we shall show that in one central case the Chamberlinian equilibrium and the constrained optimum coincide. In the same case, we shall also show that the first-best optimum has firms of the same size as in the other two solutions, and a greater number