On the Economics of Peer-to-Peer Content Distribution Systems for Large-volume Contents

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2011Tell Me a Good Story and I may lend you money,the role of narratives in peer-to-peer decisions

MICHAL HERZENSTEIN,SCOTT SONENSHEIN,and UTPAL M.DHOLAKIAThis research examines how identity claims constructed in narrativesby borrowers inﬂuence lender decisions about unsecured personal loans.Speciﬁcally,do the number of identity claims and their content inﬂu-ence lending decisions,and can they predict the longer-term perfor-mance of funded loans?Using data from the peer-to-peer lending website,the authorsﬁnd that unveriﬁable information affects lendingdecisions above and beyond the inﬂuence of objective,veriﬁable informa-tion.As the number of identity claims in narratives increases,so doesloan funding,whereas loan performance suffers,because these borrow-ers are less likely to pay back the loan.In addition,identity content playsan important role.Identities focused on being trustworthy or successfulare associated with increased loan funding but ironically are less predic-tive of loan performance than other identities(i.e.,moral and economichardship).Thus,some identity claims aim to mislead lenders,whereasothers provide true representations of borrowers.Keywords:identities,narratives,peer-to-peer lending,decision makingunder uncertainty,consumerﬁnancial decision making Tell Me a Good Story and I May Lend Y ou Money:The Role of Narratives inPeer-to-Peer Lending DecisionsThe past decade has witnessed a growing number of business models that facilitate economic exchanges between individuals with limited institutional mediation. Consumers can buy products on eBay,lend money on peer-to-peer(P2P)loan auction sites such as , and provide zero-interest“social loans”to entrepreneurs through .In all these cases,strangers decide whether to engage in an economic exchange and on what terms,using only information provided by the borrowers. *Michal Herzenstein is Assistant Professor of Marketing,Lerner College of Business and Economics,University of Delaware(e-mail: michalh@).Scott Sonenshein is Assistant Professor of Man-agement,Jones Graduate School of Business,Rice University(e-mail: scotts@).Utpal M.Dholakia is Professor of Management, Jones Graduate School of Business,Rice University(e-mail:dholakia@ ).The authors thank Rick Andrews,Richard Schwarz,and Greg Hancock for their statistical assistance.They further thank the editor John Lynch,the associate editor,and the two JMR reviewers for their insight-ful comments.Financial support from the Lerner College of Business and Economics at the University of Delaware and the Jones Graduate School of Business at Rice University is greatly appreciated.David Mick served as associate editor for this article.Objective quantitative data about exchange partners often are difﬁcult to obtain,insufﬁcient,or unreliable.As a result, decision makers may turn to subjective,unveriﬁable,but potentially diagnostic qualitative data(Michels2011). One form of qualitative data useful to decision makers in such economic exchanges are the narratives constructed by potential exchange partners.A narrative is a sequentially structured discourse that gives meaning to events that unfold around the narrator(Riessman1993).For example,a narra-tive might explain a person’s past experiences,current sit-uation,or future hopes(e.g.,Thompson1996;Wong and King2008).By providing an autobiographical sketch that explains the vicissitudes of their life,the narrative authors provide a window into how they conceptualize themselves (Gergen and Gergen1997)and a portrait of how they con-struct their identity.However,as a result of either ambiguity or the strategic use of the medium to inﬂuence others(e.g., Schau and Gilly2003),narratives offer only one of several possible interpretations of self-relevant events(Sonenshein 2010).As a result,narrators can relay interpretations of their circumstances that convey the most favorable identities (Goffman1959).©2011,American Marketing AssociationISSN:0022-2437(print),1547-7193(electronic)S138Journal of Marketing ResearchV ol.XLVIII(Special Issue2011),S138–S149Role of Narratives in Peer-to-Peer Lending Decisions S139RESEARCH MOTIVATIONS AND CONTRIBUTIONS The idea that narratives may involve the construction of a favorable identity poses two key questions for research. First,whereas narratives can provide diagnostic informa-tion to a decision maker who is considering an economic exchange,the veracity of the narrator’s story is difﬁcult to determine.Because a narrative offers the possibility of describing either an authentic,full,true self or a partial, inauthentic,misleading self,potential exchange partners are left to intuit the truth of the presentation.Accordingly a key question to consider is,given their potential for diagnostic and misleading information,to what extent do narratives inﬂuence economic exchange transactions?Previous con-sumer research has largely focused on narratives of con-sumption experiences(Thompson1996)or consumption stories(Levy1981),but scholars have not examined the role of narratives in economic exchanges.We believe that narratives may be a particularly powerful lens,in that they allow the consumer to attempt to gain better control over the exchange and thus can provide a means to help con-summate the exchange.Second,to what extent do narratives affect the perfor-mance and outcomes of an economic exchange?Narrative scholars claim that the construction and presentation of a narrative can shape its creator’s future behavior(Bruner 1990)but rarely examine the nature of this inﬂuence empir-ically.Such an examination would be critical to understand-ing how a mixture of quantitative and qualitative factors shapes outcome quality(e.g.,Hoffman and Yates2005). We examine these two questions using data from the online P2P loan auctions website,,by studying borrower-constructed narratives(particularly the identities embedded in them),the subsequent decisions of lenders, and transaction performance two years later.We deﬁne identity claims as the ways that borrowers describe them-selves to others(Pratt,Rockmann,and Kaufmann2006). Borrowers can construct an identity based on a range of ele-ments,such as religion or success.The elements become an identity claim when they enter public discourse as opposed to private cognition.With this framework,we make several contributions.First,by developing and testing theory around how nar-ratives supplement more objective sources of information that decision makers use when considering aﬁnancial trans-action,we draw attention to how narrators can intentionally exploit uncertainty and favorably shape circumstantial facts to obtain resources,such as access to money in unmediated environments.The narrative,as a supplementary,yet some-times deal-making or deal-breaking,information source for decision makers is predicated on compelling stories versus objective facts.It thus offers a means for people to recon-struct their pasts and describe their futures in positive ways. Second,by linking narratives to objective performance measures,we show how narratives may predict the longer-term performance of lending decisions.Because the deci-sion stakes are high in this unmediated and unsecured ﬁnancial arena,lenders engage in highly cognitive pro-cessing(Petty and Wegener1998).The strong disincen-tive of potentialﬁnancial loss leads to cognitive process-ing,which tends to produce accurate attributions about a person and the probabilities of future events(Osborne and Gilbert1992).Because of this motivation for accuracy,we suspect lenders use narratives to help them make invest-ment decisions.Third,from a practice perspective,the recentﬁnancial crisis has exposedﬂaws in the criteria used to make lend-ing decisions.Quantitativeﬁnancial metrics,such as credit scores,have proven unreliable for predicting the ability or likelihood of consumers to repay unsecured loans(Feldman 2009).A narrative perspective on the consummation and performance ofﬁnancial transactions offers the promise of improving systems for assessing borrowers.RESEARCH SETTINGWe conducted our research on (hereinafter, Prosper),the largest P2P loan auction site in the United States,with more than one million members and$238mil-lion in personal loans originated since its inception in March2006(as of June2011).On Prosper,borrowers and lenders never meet in person,so we can assess the role of narratives in overcoming the uncertainty that arises during ﬁnancial transactions between unacquainted actors.The process of borrowing and lending money through a loan auction on Prosper is as follows:Before posting their loan request,borrowers give Prosper permission to ver-ify relevant personal information(e.g.,household income, home ownership,bank accounts)and access their credit score from Experian,a major credit-reporting ing this and other information,such as pay stubs and income tax returns,Prosper assigns each borrower a credit grade that reﬂects the risk to lenders.Credit grades can range from AA, which indicates that the borrower is extremely low risk(i.e., high probability of paying back the loan),through A,B,C, D,and E to HR,which signiﬁes the highest risk of default. Borrowers then post loan requests for auction.When post-ing their loan auctions,borrowers choose the amount(up to $25,000)and the highest interest rate they will pay.They also may use a voluntary open-text area,with unlimited space,to write anything they want—that is,the borrower’s narrative(see Michels2011).After the listing becomes active,lenders decide whether to bid,how much money to offer,and the interest rate. A$1,000loan might beﬁnanced by one lender who lends $1,000or by40lenders,each lending$25for example. Most lenders bid the minimum amount($25)on individual loans to diversify their portfolios(Herzenstein,Dholakia, and Andrews2011).After the auction closes,listings with bids that cover the requested amount are funded.If a list-ing receives bids covering more than its requested amount, the bids with the lowest interest rates win.If the auc-tion does not receive enough bids,the request remains unfunded.Prosper administers the loan,collects payments, and receives fees of.5%to3.0%from borrowers,as well as a1%annual fee from lenders.We employed three dependent variables in our study. First,loan funding is the percentage of the loan request to receive a funding commitment from lenders.For exam-ple,if a loan request for$1,000receives bids worth$500, loan funding is50%.If it receives bids worth$2,000,loan funding equals200%.A higher loan funding value signi-ﬁes greater lender interest.Second,percentage reduction inﬁnal interest rate captures the decrease in the inter-est rate between the borrower’s maximum speciﬁed rate and theﬁnal rate.For example,if a borrower’s maximumS140JOURNAL OF MARKETING RESEARCH,SPECIAL ISSUE 2011T able 1DEFINITIONS OF IDENTITIES AND EXAMPLES FOR DATA CODINGIdentityDeﬁnitionExamplesTrustworthy (Duarte,Siegel,and Young 2009)Lenders can trust the borrower to pay back the money on time.“I am responsible at paying my bills and lending me funds would be a good investment.”(Listing #17118)Successful (Shaﬁr,Simonson,and Tversky 1993)The borrower is someone with a successful business or job/career.“I have [had]a very solid and successful career with an Aviation company for the last 13years.”(Listing #18608)Hardworking (Woolcock 1999)The borrower will work very hard to pay the loan back.“I work two jobs.I work too much really.I work 26days a month with both jobs.”(Listing #18943)Economic hardship (Woolcock 1999)The borrower is someone in need because of hardship,as a result of difﬁcult circumstances,bad luck,or other misfortunes that were,or were not,under the borrower’s control.“Unfortunately,a messy divorce and an irresponsible ex have left me with awful credit.”(Listing #20525)Moral (Aquino et al.2009)The borrower is an honest or moral person.“On paper I appear to be an extremely poor ﬁnancial risk.In reality,I am an honest,decent person.”(Listing #17237)Religious (Weaver and Agle 2002)The borrower is a religious person.“One night,the Lord awaken me and myspouse our business has been an enormous success with G-d on our side.”(Listing #21308)interest rate is 18%and the ﬁnal rate is 17%,the per-centage reduction in interest rate is 18−17 /18=5 56%.rate decreases only if the loan request receives full greater lender interest results in greater reduc-of the interest rate.Third,loan performance is the payment status of the loan two years after its origination.We further classify the types of identity claims made by prospective borrowers.Borrowers in our sample employed six identity claims in their narratives:trustworthy,economic hardship,hardworking,successful,moral,and religious.In Table 1,we provide deﬁnitions and illustrative examples of each identity claim.Borrowers provided an average of 1.53 SD =1 14 identity claims in their narratives.RESEARCH HYPOTHESESWho Is Likely to Provide More Identity Claims in Their Narratives?Narratives,when viewed as vehicles for identity work,provide opportunities for people to manage the impres-sions that others hold of them.Impression management the-ory posits that people want to create and maintain speciﬁc identities (Leary and Kowalski 1990).Narratives provide an avenue for impression management;through discourse,people can shape situations and construct identities that are designed speciﬁcally to obtain a desired outcome (Schlenker and Weigold 1992).Some scholars argue that people use narratives strategically to establish,maintain,or protect their desired identities (Rosenfeld,Giacalone,and Riordan 1995).However,the use of impression manage-ment need not automatically signal outright lying;people may select from a repertoire of self-images they genuinely believe to be true (Leary and Kowalski 1990).Nevertheless,strategic use of impression management means that,at a minimum,people select representations of their self-image that are most likely to garner support.In economic exchanges involving repeated transactions,each party receives feedback from exchange partners thateither validates or disputes the credibility of their self-constructions (Leary and Kowalski 1990),so they can determine if an identity claim has been granted.Prior transactions also offer useful information through feedback ratings and other mechanisms that convey and archive rep-utations (Weiss,Lurie,and MacInnis 2008).However,in one-time economic exchanges,such feedback is not avail-able.Instead,narrators have a single opportunity to present a convincing public view of the self,and receivers of the information have only one presentation to deem the presen-ter as credible or not.We hypothesize that in these conditions,borrowers are strategic in their identity claims.Borrowers with satisfac-tory objective characteristics are less likely to construct identity claims to receive funding;they feel their case stands ﬁrmly on its objective merits alone.In contrast,borrowers with unsatisfactory objective characteristics may view narratives as an opportunity to inﬂuence the attribu-tions that lenders make,because in narratives,they can counter past mistakes and difﬁcult circumstances.In this scenario,borrowers make identity claims that offset the attributions made by lenders about the borrower being fundamentally not a creditworthy person.These disposi-tional attributions are often based on visible characteristics (Gilbert and Malone 1995).The most relevant objective characteristic of borrowers is the credit grade assigned by Prosper,derived from the borrower’s personal credit history (Herzenstein,Dholakia,and Andrews 2011).With more than one identity claim,borrowers can present a more com-plex,positive self to counteract negative objective informa-tion,such as a low credit grade.Thus:H 1:The lower the borrower’s credit grade,the greater isthe number of identities claimed by the borrower in the narrative.Role of Narratives in Peer-to-Peer Lending Decisions S141Impact of the Number of Identity Claims onLenders’DecisionAlthough economists often predict that unveriﬁable information does not matter(e.g.,Farrell and Rabin1996), we suggest that the number of identity claims in a bor-rower’s narrative play a role in lenders’decision making, for at least two reasons.First,borrower narratives with too few identities may fail to resolve questions about the borrower’s disposition.If a borrower fails to provide suf-ﬁcient diagnostic information for lenders to make attri-butions about the borrower(Cramton2001),lenders may suspect that the borrower lacks sufﬁcient positive or dis-tinctive information or is withholding or hiding germane information.Second,the limited diagnostic information provided by fewer identity claims limits a decision maker’s ability to resolve outcome uncertainties.Research on perceived risk supports this reasoning;decision makers gather informa-tion as a risk-reduction strategy and tend to be risk averse in the absence of sufﬁcient information about the decision (e.g.,Cox and Rich1964).In the P2P lending arena,the loan request and evaluation process unfold online with-out any physical interaction between the parties.Further-more,on Prosper,borrowers are anonymous(real names and addresses are never revealed).This lack of seemingly relevant information is especially salient,because many decision makers view unmediated online environments as ripe for deception(Caspi and Gorsky2006).To the extent that the identity claims presented in a narrative reduce uncertainty about a borrower,lenders should be more likely to view the listing favorably,increase loan funding,and decrease theﬁnal interest rate.Therefore,the number of identity claims in a borrower’s narrative may serve as a heuristic for assessing the borrower’s loan application and lead to greater interest in the listing.Although we suggest that the number of identities bor-rowers claim result in favorable lending decisions,we also argue that these identity claims may persuade lenders erroneously,such that lenders fund loans with a lower likelihood of repayment.Borrowers can use elaborate multiple-identity narratives to craft“not-quite-true”stories and make promises they mightﬁnd difﬁcult to keep.More generally,a greater number of identity claims suggests that borrowers are being more strategic and positioning them-selves in a manner they believe is likely to resonate with lenders,as opposed to presenting a true self.Therefore,we posit that,consciously or not,borrowers who construct sev-eral identities may have more difﬁculty fulﬁlling their obli-gations and be more likely to fall behind on or stop loan repayments altogether.Thus,despite the high stakes of the decision,lenders swayed by multiple identities are more likely to fall prey to borrowers that underperform or fail (Goffman1959).H2:Controlling for objective,veriﬁable information,the more identities borrowers claim in their loan requests,the morelikely lenders are to(a)fund the loan and(b)reduce itsinterest rate,but then(c)the lower is the likelihood of itsrepayment.Role of the Content of Identity Claims onLender Decision Making and Loan PerformanceWe also examine the extent to which select identities affect lenders’decision making and the longer-term per-formance of loans.With a limited theoretical basis for determining the types of identities most likely to inﬂu-ence lenders’decision making,this part of our study is exploratory.Research on trust offers a promising starting point(Mayer,Davis,and Schoorman1995),because it sug-gests that identities may reduce dispositional uncertainty and favorably inﬂuence lenders.Trust is a crucial element for the consummation of an economic exchange(Arrow 1974).Scholars theorize that trust involves three compo-nents:integrity(borrowers adhere to principles that lenders accept),ability(borrowers possess the skills necessary to meet obligations),and benevolence(borrowers have some attachment to lenders and are inclined to do good)(Mayer, Davis,and Schoorman1995).We theorize that trustworthy,religious,and moral iden-tities increase perceptions of integrity because they lead lenders to believe that borrowers ascribe to the lender-endorsed principle of fulﬁlling obligations,either directly (trustworthy)or indirectly by adhering to a philosophy (religious or moral).Speciﬁcally,a moral identity tells potential lenders that the person has“a self-conception organized around a set of moral traits”(Aquino et al.2009, p.1424),which should increase perceptions of integrity.A religious identity signals a set of role expectations to which a person is likely to adhere,and though religions vary in the content of these expectations(Weaver and Agle 2002),many of them include principles oriented against lying or stealing and toward honoring contractual agree-ments.A hardworking identity should increase perceptions of integrity,because hardworking people are determined and dependable,which often makes them problem solvers (Witt et al.2002),meaning that they will do their best to meet their obligations,a disposition likely to resonate with lenders.We also reason that the religious and moral identities invoke in lenders a sense of benevolence,which is a foun-dational principle of many religions and moral philoso-phies.Similarly,the economic hardship identity may invoke benevolence,because the borrower exhibits forthrightness about his or her past mistakes and thus suggests to lenders that the borrower is trying to create a meaningful relation-ship based on transparency.We theorize that an identity claim of success can increase perceptions of ability and the belief that the narrator is capable of fulﬁlling promises(Butler1991).Lenders are more likely to lend money to a borrower if they perceive that the person is capable of on-time repayment(Newall and Swan2000).A successful identity likely describes the past or present,but it also can serve as an indication of a probable future(i.e.,the borrower will continue to be successful),which helps“ﬁll in the blanks”about the bor-rower in a positive way.In contrast,economic hardship likely constructs the borrower as someone who has had a setback,which ultimately undermines perceptions of ability and thus negatively affects lenders’decisions.We have offered some preliminary theory in support of these speciﬁc relationships between identity content and loan funding/interest rate reductions,but this examinationS142JOURNAL OF MARKETING RESEARCH,SPECIAL ISSUE2011remains exploratory,so we pose these relationships as exploratory research questions(ERQ):ERQ1:Which types of identity claims inﬂuence lending deci-sions,as indicated by(a)an increase in loan fundingand(b)a decrease in theﬁnal interest rate?We also explore the impact of the content of identity claims on loan performance.We envision two potential sce-narios.In theﬁrst,identities are diagnostic of the borrower or serve as self-fulﬁlling prophecies.Examining the ability aspect of trustworthiness,we anticipate a negative relation between an economic hardship identity and loan perfor-mance(borrowers validate their claim of setbacks)but a positive relation between a successful identity and loan per-formance(borrowers prove their claim of past success). Moreover,we expect the four integrity-related identities—trustworthy,hardworking,moral,and religious—to indicate better loan performance.After a self-presentation as having integrity,the borrower probably has a strong psychological desire for consistency between the narrative and his or her actions(Cialdini and Trost1998).That is,in their narra-tives,borrowers may make an active,voluntary,and public commitment that psychologically binds them to a partic-ular set of beliefs and subsequent behaviors(Berger and Heath2007).Because these four identities speak to funda-mental self-beliefs versus predicted outcomes(e.g.,success or hardship),they can strongly motivate borrowers to live up to their claims.Thus these identities,regardless of their accuracy,can become true and predict the performance of the lending decision.In the other scenario,however,identities improve the lender’s impression of the borrower,thereby allowing bor-rowers to exert control over the provided impressions (Goffman1959).Borrowers(or narrators,more generally) construct positive impressions and may misrepresent them-selves and send signals that may not be objectively war-ranted.Despite the belief that self-constructing identities are helpful for a lending decision,they actually may have no impact or even be harmful to lenders.These mixed pos-sibilities lead to another exploratory research question: ERQ2:How are the content of identity claims and loan perfor-mance related?STUDYDataOur data set consists of1,493loan listings posted by borrowers on Prosper in June2006and June2007.We extracted this data set using a stratiﬁed random sampling ing a web crawler,we extracted all loan listings posted in June2006and June2007(approximately5,400 and12,500listings,respectively).A signiﬁcant percentage of borrowers on Prosper have very poor credit histories, and most loan requests do not receive funding.To avoid overweighting high-risk borrowers and unfunded loans,we sampled an equal number of loan requests from each credit grade.To do so,weﬁrst separated funded loan requests from unfunded ones,then divided each group by the seven credit grades assigned by Prosper.We also eliminated all loan requests without any narrative text,for three reasons. First,including loan requests without narratives could con-found the borrower’s choice to write something other than narratives in the open text box with the choice to write nothing at all.Second,the vast majority of listings lack-ing a narrative do not receive funding.Third,loan requests without text represent only9%of all loans posted in June 2006and4%of those posted in June2007.We nevertheless used the“no text”loans in our robustness check.We randomly sampled posts from the14subgroups (2funding status×7credit grades).In2006,we sampled 40listings from each subgroup(until data were exhausted) to obtain513listings;in2007,we sampled70listings from each subgroup to obtain980listings,for a total of 1,493listings.Each listing includes the borrower’s credit grade,requested loan amount,maximum interest rate,loan funding,ﬁnal interest rate of funded loans,payback sta-tus of funded loans after two years,and open-ended text data.Before combining the data from2006and2007,we tested for a year effect but found none,which supports their combination.Dependent VariablesTheﬁrst dependent variable,loan funding,ranges from 0%to905%in our data set,but requiring an equal inclu-sion of all credit ratings skews these statistics.The mean percentage funded(including all listings)is105.74%(SD= 129 2)and that for funded listings is205.45%(SD=119 6). Because it was skewed,we log-transformed loan fund-ing as follows:Ln(percent funded+1).The second depen-dent variable,percentage reduction in theﬁnal interest rate, ranges from0%to56%in our data set.The mean per-centage reduction in interest rate for all listings is6.4% (SD=10 7)and for funded listings is11.88%(SD=12 75). Because the distribution is skewed,we log-transformed it (we provide the distributionﬁgures in the Web Appendix, /jmrnov11).The third dependent variable is loan performance,mea-sured two years after loan funding.For each funded loan in our data set,we obtained data about whether the loan was paid ahead of schedule and in full(31.1%of funded list-ings),was current and paid as scheduled(40.5%),involved payments between one and four months late(7.1%),or had defaulted(21.3%).This dependent variable may appear ordered,but the likelihood ratio tests reveal that a multino-mial logit model fares better than an ordered logit model for analyzing these data(for both the number and content of identities).Thus,in the following analysis,we employ a multinomial logit model.Independent VariablesWe read approximately one-third of all narratives and developed our inductively derived list of six identity claims (Miles and Huberman1994):trustworthy,economic hard-ship,hardworking,successful,moral,and religious,as we deﬁne in Table1.Two research assistants examined the same data and determined these six identities were exhaustive.Next,ﬁve additional pairs of research assistants (10total)coded the entire data set.We coded each iden-tity as a dichotomous variable that receives the value of1 if the identity claim was present in a borrower’s narrative and0if otherwise.A pair of research assistants read each listing in the data set,independently atﬁrst,then discussed them to determine the uniﬁed code for each listing.Accord-ing to20randomly sampled listings from our data set,used。

英语经济理论学习30题

英语经济理论学习30题1. In a market economy, the allocation of resources is mainly determined by _____.A. government planningB. market forcesC. traditional customsD. random events答案：B。

本题主要考查市场经济中资源分配的决定因素。

选项A，政府规划在计划经济中起主导作用，而市场经济主要依靠市场力量。

选项C，传统习俗对资源分配的影响较小。

选项D，随机事件不是市场经济中资源分配的主要决定因素。

市场力量，如供求关系等，在市场经济中起着关键作用。

2. The law of demand states that, other things being equal, as the price of a good rises, the quantity demanded _____.A. risesB. fallsC. remains unchangedD. increases sharply答案：B。

本题考查需求定律。

根据需求定律，在其他条件不变的情况下，商品价格上升，需求量会下降。

选项A 价格上升需求量上升不符合需求定律。

选项C 需求量保持不变也不符合。

选项D 需求量大幅增加同样不符合需求定律。

3. Supply refers to the _____.A. amount of a good that producers are willing and able to sell at a given priceB. total amount of a good that exists in the economyC. amount of a good that consumers are willing to buyD. amount of a good that the government wants to produce答案：A。

2022年考研考博-考博英语-北京科技大学考试预测题精选专练VII(附带答案)卷1

2022年考研考博-考博英语-北京科技大学考试预测题精选专练VII（附带答案）第1套一.综合题(共25题)1.单选题The disagreement over trade restrictions could seriously（） relations between the two countries.问题1选项A.tumbleB.jeopardizeC.manipulateD.intimidate【答案】B【解析】考查动词辨析。

A项tumble“摔倒，倒塌”，B项jeopardize“危害，使陷危地”，C项manipulate“操作，操纵”，D项intimidate“恐吓，威胁”。

根据句子关键词disagreement over trade restrictions（关于贸易限制的分歧）和relations（关系）可猜测，空格部分表示“贸易分歧恶化了关系”，因此四个选项中只有jeopardize符合。

句意：贸易限制问题上的分歧可能严重危及两国关系。

因此，该题选择B项正确。

2.单选题The belief that it’s healthy to let off steam no longer（）for we are working under heavy pressure.问题1选项A.holdsB.carriesC.takesD.stands【答案】C【解析】考查动词辨析。

A项hold“拥有，持有”，B项carry“拿，携带”，C项take“行得通，花费”，D项stand“站立，位于”。

根据句子可知，空格部分是和名词belief（信念）构成主谓，把四个选项分别代入，只有take符合。

句意：因为我们在巨大的压力下工作，所以不再相信释放压力是有益健康的。

因此，该题选择C项正确。

3.单选题John has such（）power that his friends always behave in the way that he wants them to. 问题1选项A.convincingB.feasibleC.operationalD.manipulative【答案】A【解析】考查形容词辨析。

研究生公共英语教材阅读B第3、4、10、11、14课文原文及翻译

Unite 3 Doctor’s Dilemma: Treat or Let Die?Abigail Trafford1. Medical advances in wonder drugs, daring surgical procedures, radiation therapies, and intensive-care units have brought new life to thousands of people. Yet to many of them, modern medicine has become a double-edged sword.2. Doctor’s power to treat with an array of space-age techniques has outstripped the body’s capacity to heal. More medical problems can be treated, but for many patients, there is little hope of recovery. Even the fundamental distinction between life and death has been blurred.3. Many Americans are caught in medical limbo, as was the South Korean boxer Duk Koo Kim, who was kept alive by artificial means after he had been knocked unconscious in a fight and his brain ceased to function. With the permission of his family, doctors in Las Vegas disconnected the life-support machines and death quickly followed.4. In the wake of technology’s advances in medicine, a heated debate is taking place in hospitals and nursing homes across the country --- over whether survival or quality of life is the paramount goal of medicine.5. “It gets down to what medicine is all about, ” says Daniel Callahan, director of the Institute of Society, Ethics, and the Life Sciences in Hastings-on-Hudson, New York. “Is it really to save a life? Or is the larger goal the welfare of the patient?”6. Doctors, patients, relatives, and often the courts are being forced to make hard choices in medicine. Most often it is at the two extremes of life that these difficultyethical questions arise --- at the beginning for the very sick newborn and at the end for the dying patient.7. The dilemma posed by modern medical technology has created the growing new discipline or bioethics. Many of the country’s 127 medical s chools now offer courses in medical ethics, a field virtually ignored only a decade ago. Many hospitals have chaplains, philosophers, psychiatrists, and social workers on the staff to help patients make crucial decisions, and one in twenty institutions has a special ethics committee to resolve difficult cases.Death and Dying8. Of all the patients in intensive-care units who are at risk of dying, some 20 percent present difficult ethical choices --- whether to keep trying to save the life or to pull back and let the patient die. In many units, decisions regarding life-sustaining care are made about three times a week.9. Even the definition of death has been changed. Now that the heart-lung machine can take over the functions of breathing and pumping blood, death no longer always comes with the patient’s “last gasp” or when the heart stops beating. Thirty-one states and the District of Columbia have passed brain-death statutes that identify death as when the whole brain ceases to function.10. More than a do zen states recognize “living wills” in which the patients leave instructions to doctors not to prolong life by feeding them intravenously or by other methods if their illness becomes hopeless. A survey of California doctors showed that 20 to 30 percent were following instructions of such wills. Meanwhile, the hospicemovement, which its emphasis on providing comfort --- not cure --- to the dying patient, has gained momentum in many areas.11. Despite progress in society’s understanding of death and dying, t heory issues remain. Example: A woman, 87, afflicted by the nervous-system disorder of Parkinson’s disease, has a massive stroke and is found unconscious by her family. Their choices are to put her in a nursing home until she dies or to send her to a medical center for diagnosis and possible treatment. The family opts for a teaching hospital in New York city. Tests show the woman’s stroke resulted from a blood clot that is curable with surgery. After the operation, she says to her family: “Why did you bring me back to this agony?” Her health continues to worsen, and two years later she dies.12. On the other hand, doctors say prognosis is often uncertain and that patients, just because they are old and disabled, should not be denied life-saving therapy. Ethicists also fear that under the guise of medical decision not to treat certain patients, death may become too easy, pushing the country toward the acceptance of euthanasia.13. For some people, the agony of watching high-technology dying is too great. Earlier this year, Woodrow Wilson Collums, a retired dairyman from Poteet, Texas, was put on probation for the mercy killing of his older brother Jim, who lay hopeless in his bed at a nursing home, a victim of severe senility resul ting from Alzheimer’s disease. After the killing, the victim’s widow said: “I think God, Jim’s out of his misery. I hate to think it had to be done the way it was done, but I understand it. ”Crisis in Newborn Care14. At the other end of the life span, technology has so revolutionized newborn carethat it is no longer clear when human life is viable outside the womb. Newborn care has got huge progress, so it is absolutely clear that human being can survive independently outside the womb. Twenty-five years ago, infants weighting less than three and one-half pounds rarely survived. The current survival rate is 70 percent, and doctors are “salvaging” some babies that weigh only one and one-half pounds. Tremendous progress has been made in treating birth deformities such as spina bifida. Just ten years ago, only 5 percent of infants with transposition of the great arteries --- the congenital heart defect most commonly found in newborns --- survived. Today, 50 percent live.15. Yet, for many infants who owe their lives to new medical advances, survival has come at a price. A significant number emerge with permanent physical and mental handicaps.16. “The question of treatment and nontreatment of seriously ill newborns is not a single one,”says Thomas Murray of the Hastings Center. “But I feel strongly that retardation or the fact that someone is going to be less than perfect is not good grounds for allowing an infant to die.”17. For many parents, however, the experience of having a sick newborn becomes a lingering nightmare. Two years ago, an Atlanta mother gave birth to a baby suffering from Down’s Syndrome, a form of mental retardation; the child also had blocked intestines. The doctors rejected the parents’ plea not to operate, and today the child, severely retarded, still suffers intestinal problems.18. “Every time Melanie has a bowel movement, she cries,” explains her mother.“She’s not able to take care of herself, and we won’t live forever. I wanted to save her from sorrow, pain, and suffering. I don’t understand the emphasis on life at all costs, and I’m very angry at the doctors and the hospital. Who will take care of Melanie after we’re gone? Where will you doctors be then?”Changing Standards19. The choices posed by modern technology have profoundly changed the practice of medicine. Until now, most doctors have been activists, trained to use all the tools in their medical arsenals to treat disease. The current trend is toward nontreatment as doctors grapple with questions not just of who should get care but when to take therapy away.20. Always in the background is the threat of legal action. In August, two California doctors were charged with murdering a comatose patient by allegedly disconnecting the respirator and cutting off food and water. In 1981, a Massachusetts nurse was charged with murdering a cancer patient with massive doses of morphine but was subsequently acquitted.21. Between lawsuits, government regulations, and patients’ rights, many doctors feel they are under siege. Modern technology actually has limited their ability to make choices. More recently, these actions are resolved by committees.Public Policy22. In recent years, the debate on medical ethics has moved to the level of national policy. “It’s just beginning to hit us that we don’t have unlimited resources,” says Washington Hospital Center’s Dr. Lynch. “You can’t talk about ethics without talkingethics without talking about money.”23. Since 1972. Americans have enjoyed unlimited access to a taxpayer-supported, kidney dialysis program that offers life-prolonging therapy to all patients with kidney failure. To a number of police analysts, the program has grown out of control --- to a $1.4billion operation supporting 61,000 patients. The majority are over 50, and about a quarter have other illness, such as cancer or heart disease, conditions that could exclude them from dialysis in other countries.24. Some hospitals are pulling back from certain lifesaving treatment. Massachusetts General Hospital, for example, has decided not perform heart transplants on the ground that the high costs of providing such surgery help too few patients. Burn units --- through extremely effective --- also provide very expensive therapy for very few patients.25. As medical scientists push back the frontiers of therapy, the moral dilemma will continue to grow for doctors and patients alike, making the choice of to treat the basic question in modern medicine.1. 在特效药、风险性手术进程、放疗法以及特护病房方面的医学进展已为数千人带来新生。

2024年高二英语可持续发展策略单选题40题

2024年高二英语可持续发展策略单选题40题1.Sustainable development aims to achieve a balance between economic growth, social progress and environmental protection. The word "sustainable" is an _____.A.nounB.verbC.adjectiveD.adverb答案：C。

“sustainable”意思是“可持续的”，是形容词。

A 选项“noun”是名词；B 选项“verb”是动词；D 选项“adverb”是副词。

本题考查词汇的词性判断。

2.We should take _____ measures to protect the environment.A.effectB.effectiveC.effectivelyD.effected答案：B。

“effective”是形容词“有效的”，修饰名词“measures”。

A 选项“effect”是名词“影响”；C 选项“effectively”是副词“有效地”；D 选项“effected”是动词过去分词“产生”。

本题考查形容词的用法。

3.The government is committed to promoting _____ development.A.sustainB.sustainableC.sustainablyD.sustained答案：B。

“sustainable”是形容词“可持续的”，修饰名词“development”。

A 选项“sustain”是动词“维持”；C 选项“sustainably”是副词“可持续地”；D 选项“sustained”是动词过去分词“持续的”。

本题考查形容词修饰名词的用法。

4._____ use of resources is crucial for sustainable development.A.EfficientB.EfficiencyC.EfficientlyD.Efficiencies答案：A。

经济学导论英语知识点总结

经济学导论英语知识点总结Economics is the study of how individuals, firms, and societies allocate their limited resources to satisfy their unlimited wants. It is a social science that analyzes the production, distribution, and consumption of goods and services. Here are some key points to understand about economics:1. Scarcity and ChoiceScarcity is the fundamental economic problem. It means that resources are limited, while human wants and needs are unlimited. As a result, individuals, firms, and societies must make choices about how to allocate their scarce resources to satisfy their wants and needs. This leads to the concept of opportunity cost, which is the value of the next best alternative that is given up when a choice is made.2. Types of EconomicsThere are two main types of economics: microeconomics and macroeconomics. Microeconomics focuses on the behavior of individual agents, such as consumers, firms, and workers, and how they make decisions about the allocation of resources. Macroeconomics, on the other hand, looks at the economy as a whole, considering factors such as inflation, unemployment, and economic growth.3. Supply and DemandSupply and demand are the forces that drive the market. The law of demand states that, all else being equal, as the price of a good or service increases, the quantity demanded decreases, and vice versa. The law of supply states that, all else being equal, as the price of a good or service increases, the quantity supplied increases, and vice versa. The intersection of the supply and demand curves gives us the equilibrium price and quantity for a particular good or service.4. ElasticityElasticity measures the responsiveness of quantity demanded or supplied to a change in price. If the quantity demanded or supplied is very responsive to a change in price, we say that it is elastic. If it is not very responsive, we say that it is inelastic. Elasticity is important for understanding how changes in price affect consumer and producer behavior.5. Market StructuresThere are different types of market structures, each with its own characteristics. These include perfect competition, monopoly, monopolistic competition, and oligopoly. Perfect competition is a market structure with many small firms, identical products, and no barriers to entry or exit. Monopoly is a market structure with a single seller and no close substitutes. Monopolistic competition is a market structure with many firms selling similar but notidentical products. Oligopoly is a market structure with a few large firms that dominate the market.6. Economic SystemsThere are different types of economic systems, each with its own way of allocating resources. These include traditional, command, market, and mixed economies. In a traditional economy, economic decisions are based on customs and traditions. In a command economy, economic decisions are made by the government. In a market economy, economic decisions are made by individuals and firms acting in their own self-interest. In a mixed economy, economic decisions are made by a combination of government and private individuals and firms.7. Factors of ProductionThe factors of production are the resources used to produce goods and services. They include land, labor, capital, and entrepreneurship. Land refers to all natural resources, such as water, minerals, and forests. Labor refers to the physical and mental effort of human beings. Capital refers to the tools, equipment, and machinery used in production. Entrepreneurship refers to the ability to organize and manage the other factors of production.8. Gross Domestic Product (GDP)GDP is one of the most important indicators of the health of an economy. It measures the total value of all goods and services produced within a country's borders over a specific period of time. GDP can be calculated using three different approaches: the production approach, the income approach, and the expenditure approach. It can also be adjusted for inflation to give us real GDP, which measures the value of goods and services produced in constant prices.9. Fiscal PolicyFiscal policy is the use of government spending and taxation to influence the economy. Expansionary fiscal policy involves increasing government spending or reducing taxes to stimulate economic growth. Contractionary fiscal policy involves reducing government spending or increasing taxes to slow down economic growth. Fiscal policy is a powerful tool for stabilizing the economy and is often used in combination with monetary policy.10. Monetary PolicyMonetary policy is the use of interest rates and money supply to influence the economy. Expansionary monetary policy involves lowering interest rates or increasing the money supply to stimulate economic growth. Contractionary monetary policy involves raising interest rates or reducing the money supply to slow down economic growth. Monetary policy is the responsibility of the central bank in most countries and is often used in combination with fiscal policy.11. International TradeInternational trade is the exchange of goods and services between countries. It allows countries to specialize in the production of goods and services in which they have a comparative advantage and then trade with other countries to obtain goods and services in which they do not have a comparative advantage. International trade can increase economic efficiency and lead to higher standards of living for all trading partners.12. Economic GrowthEconomic growth is the increase in the production of goods and services over time. It is measured by the growth rate of GDP. Economic growth is important because it leads to higher standards of living, lower unemployment, and greater economic opportunity. Factors that contribute to economic growth include improvements in technology, increases in the quantity and quality of the factors of production, and increases in human capital.In conclusion, economics is a complex and fascinating field of study that is essential for understanding how individuals, firms, and societies allocate their limited resources to satisfy their unlimited wants and needs. By understanding the key points discussed in this article, you can gain a deeper appreciation for the forces that drive the economy and the tools that policymakers use to manage it. Whether you are a student, a business owner, or a policymaker, a solid understanding of economics is crucial for making informed decisions in the modern world.。

【2021年】山西省吕梁市大学英语6级大学英语六级真题(含答案)

【2021年】山西省吕梁市大学英语6级大学英语六级真题(含答案)学校:________ 班级:________ 姓名:________ 考号:________一、1.Writing(10题)1. For this part, you are allowed 30 minutes to write a short essay entitled On Aging Population. You should write at least 150 words based on the chart and outline given below:1. 目前老龄化现象很严重2. 这种现象可能产生的社会影响和后果3. 你的建议On Aging Population2. Directions: For this part, you are allowed thirty minutes to write a letter of application. You should write at least 150 words, and base your letter on the situation given in Chinese:假如你是David Yang/Mary Yang,是U大学即将毕业的本科生，向某公司写一信求职信。

先描述自己的一些基本情况，包括学生、专业、在校学习成绩、英语水平、个人爱好、是否有相关的工作经历。

然后描述你对将来工作的预期，包括工作职务和工资水平等细节。

3. For this part, you are allowed 30 minutes to write a short essay on the topic of Should Schools Offer Handwriting Lessons?. You should write at least 150 words according to the outline given below.1. 有人认为学校应该开设书法课2. 有人则反对3. 我的看法Should Schools Offer Handwriting Lessons?4. Directions: For this part, you are allowed 30 minutes to write a composition on the topic: Overseas Study at an Early Age. You should write at least 150 words following the outline given below:1. 目前很多父母在子女高中毕业前就送他们出国学习2．形成这种趋势的原因3．我对此的看法Overseas Study at an Early Age5. For this part, you are allowed 30 minutes to write a composition on the topic Economic Development and Moral Decline. You should write at least 150 words and you should base your composition on the outline (given in Chinese) be low:1. 近年来我国经济建设取得了很大成就;2. 但与此同时,社会风气随着经济的发展也日益下降3. 我的观点……6. For this part, you are allowed 30 minutes to write a composition on the topic Test for National Civil Servants. You should write at least 150 words according to the outline given below in Chinese:1．近几年兴起了一股国家公务员考试(Test for National Civil Servants)热2．产生这种现象的原因3．我的看法Test for National Civil Servants7. 1.老一辈常说,能力比相貌重要2. 如今很多人却认为相貌比能力重要3. 你的看法8. For this part, you are allowed 30 minutes to write A Letter of complaint about the noise around your school. You should write at least 150 words according to the outlines given below in Chinese.假设你是李明，深受学校附近一家工厂的噪音之苦，现在你写信给学校领导反映情况，内容包括以下几点：1．噪音污染的现状和严重程度2．引起噪音的原因3．你希望校领导能尽快采取措施解决问题A Letter of Complaint9. Directions: For this part, you are allowed 30 minutes to write a composition on the topic The Reading Preferences of Students at a Chinese University in 2006. You should write at least 150 words following the outline given below.1. 描述图表的变化。

《国际经济学》(双语)试卷1参考答案

《国际经济学》（双语）试卷1参考答案Ⅰ. Explain the following terms (30 points, 3 points/term)parative advantage:A country has a comparative advantage in producing a good if the opportunity cost of producing that good in terms of other goods is lower in that country than it is in other countries(3 points).2.Specific factors model: It assumes an economy that produces two goods and the labor is a mobile factor that can move between sectors, other factors are assumed to be specific, that is, they can be used only in the production of particular goods(3 points).3．Heckscher-Ohlin theory: it is also referred to as the factor-proportions theory, the theory emphasizes the interplay between the proportions in which different factors of production are available in different countries and the proportions in which they are used in producing different goods(3 points).4.Leontief paradox: the United States would be an exporter of capital-intensive goods and an importer of labor-intensive goods. Surprisingly, however, this was not the case, the economist Leontief found that U.S. exports were less capital-intensive than U.S. imports. This result is known as the Leontief paradox. It is the single biggest piece of evidence against the factor-proportions theory(3 points).5.Official international reserves: Official international reserves are foreign assets held by central banks as a cushion against national economic misfortune. At one time official reserves consisted largely of gold, but today central banks' reserves include substantial foreign financial assets, particularly U.S. dollar assets such as Treasury bills(3 points).6.The official settlements balance: the official settlements balance or the balance of payments. This balance is the sum of the current account balance, the capital account balance, the nonreserve portion of the financial account balance, and the statistical discrepancy, and it indicates the payments gap that official reserve transactions need to cover(3 points).7.Foreign exchange option: A foreign exchange option gives its owner the right to buy or sell a specified amount of foreign currency at a specified price at any time up to a specified expiration date. The other party to the deal, the option's seller, is required to sell or buy the foreign currency at the discretion of the option's owner, who is under no obligation to exercise his right(3 points).8.Interest parity condition: The condition that the expected returns on deposits of any twocurrencies are equal when measured in the same currency is called the interestparity condition. It implies that potential holders of foreign currency deposits view them all as equally desirable assets.9.Fisher effect: This long-run relationship between inflation and interest rates is called the Fisher effect. Fisher effect tells us that all else equal, a rise in a country's expected inflation rate will eventually cause an equal rise in the interest rate that deposits of its currency offer. Similarly, a fall in the expected inflation rate will eventually cause a fall in the interest rate(3 points).10.Long run analysis: The long run analysis of an economic event allows for the complete adjustment of the price level (which may take a long time) and for full employment of all factors of production(3 points).II. Single-Choice Questions（15 points, 1.5points/Question）1. b2. d3. c4. a5. b6. a7. d8. a9. c 10. aⅢ.Questions and problems（40 points, 8 points/Question）1.What are the three types of international transaction recorded in the balance of payments(8 points)?Answer: the three types of international transactions are current account, financial account and capital account(3 points). Transactions that involve the export or import of goods or services and therefore enter directly into the current account. Transactions that involve the purchase or sale of financial assets. An asset is any one of the forms in which wealth can be held, such as money, stocks, factories, or government debt. The financial account of the balance of payments records all international purchases or sales of financial assets. Certain other activities resulting in transfers of wealth between countries are recorded in the capital account(5 points).2. In the United States where land is cheap, the ratio of land to labor used in cattle rising is higher than that of land used in wheat growing. But in more crowded countries, where land is expensive and labor is cheap, it is common to raise cows by using less land and more labor than Americans use to grow wheat. Can we still say that raising cattle is land intensive compared with farming wheat? Why or why not(8 points)?Answer: The definition of cattle growing as land intensive depends on the ratio of land to labor used in production, not on the ratio of land or labor to output(3 points). The ratio of land to labor in cattle exceeds the ratio in wheat in the United States, implying cattle is land intensive in the United States. Cattle is land intensive in other countries too if the ratio of land to labor in cattle production exceeds the ratio in wheat production in that country. The comparison between another country and the United States is less relevant for answering the question(5 points).3. Suppose the dollar interest rate and the pound sterling interest rate are the same, 5 percent per year. What is the relation between the current equilibrium $/£ exchange rate and its expected future level? Suppose the expected future $/£ exchange rate, $1.52 per pound, remains constant as Britain's interest rate rises to 10 percent per year. If the U.S. interest rate also remains constant, what is the new equilibrium$/£ exchange rate(8 points)?Answer: The current equilibrium exchange rate must equal its expected future level since, with equality of nominal interest rates, there can be no expected increase or decrease in the dollar/pound exchange rate in equilibrium(3 points). If the expected exchange rate remains at $1.52 per pound and the pound interest rate rises to 10 percent, then interest parity is satisfied only if the current exchange rate changes such that there is an expected appreciation of the dollar equal to 5 percent. This will occur when the exchange rate rises to $1.60 per pound (a depreciation of the dollar against the pound) (5 points).4. What are the real exchange rate and nominal exchange rate, and their differences(8 points)?Answer: the real exchange rate is the relative price of two output baskets, nominal exchange rate is the relative price of two currencies(3 points).The real exchange rate between two countries' currencies is a broad summary measure of the prices of one country's goods and services relative to the other's. the prediction of PPP is that real exchange rates never change, at least not permanently. Real exchange rates are defined, however, in terms of nominal exchange rates and price levels(5 points).5:Give a example to explain foreign exchange swap(8 points).Answer: foreign exchange swap is a spot sale of a currency combined with a forward repurchase of the currency(3 points). For example, a multinational company has just received $1 million from sales and knows it will have to pay those dollars to a California supplier in three months. The company's asset-management department would meanwhile like to invest the $1 million in Swiss francs. A three-month swap of dollars into Swiss francs may result in lower brokers' fees than the two separate transactions of selling dollars for spot Swiss francs and selling the Swiss francs for dollars on the forward market(5 points).Ⅳ.An economy can produce good 1 using labor and capital and good 2 using labor and land. The total supply of labor is 100 units.The marginal product of labor production are70 0.69 0.49 800.66 0.46 900.63 0.43 1000.60 0.40Questions: a. Suppose that the price of good 2 relative to that of good 1 is 2. Determine graphically the wage rate and the allocation of labor between the two sectors (5 points).b. Suppose that the relative price of good 2 falls to 1. Determine the wage rate and the allocation of labor between the two sectors (5 points).c. Calculate the effects of the price change on the income of the specific factors in sectors 1 and 2(5 points).Answer: a. With the assumption that labor is freely mobile between sectors, it will move from the low-wage sector to the high-wage sector until wages are equalized. So in equilibrium, the wage rate is equal to the value of labor ’s marginal product.2/122211=⨯=⨯P P P MPL P MPLThe abscissa of point of intersection illustrated above should be at L1=30. The labor allocation between the sectors is L1=30 and L2=70. The wage rate is 0.98(5 points). b. The relative decline in the price of good 2 caused labor to be reallocated: labor is drawn out of production of good 2 and enters production of good 1 (Ｌ1=60, L2=40). And the wage rate is equal to 0.74(5 points).c. With the relative price change from P2/P1=2 to P2/P1=1, the price of good 2 has fallen by 50 percent, while the price of good 1 has stayed the same. Wages have fallen too, but by less than the fall in P2 (wages fell approximately 25 percent). Thus, the real wage relative to P2 actually rises while real wage relative to P1 falls. Hence, to determine the welfare consequence for workers, the information about their consumption shares of good 1 and good 2 is needed(5 points).。

美国财政部长盖特纳北京大学演讲中英文全文

The United States and China, Cooperating for Recovery and GrowthThe United States and China, Cooperating for Recovery and GrowthTreasury Secretary Timothy F. GeithnerSpeech at Peking University - Beijing, ChinaIt is a pleasure to be back in China and to join you here today at this great university.I first came to China, and to Peking University, in the summer of 1981 as a college student studying Mandarin. I was here with a small group of graduate and undergraduate students from across the United States. I returned the next summer to Beijing Normal Univ ersity.We studied reasonably hard, and had the privilege of working with many talented professors, some of whom are here today. As we explored this city and traveled through Eastern China, we had the chance not just to understand more about your history and your aspirations, but also to begin to see the United States through your eyes.Current Challenges and RisksThe world economy is going through the most challenging economic and financial stress in generations.In fact, what distinguishes the current crisis is not just its global scale and its acute severity, but the size and speed of the global response.At the G-20 Leaders meeting in London in April, we agreed on an unprecedented program of coordinated policy actions to support growth, to stabilize and repair the financial system, to restore the flow of credit essential for trade and investment, to mobilize financial resources for emerging market economies through the international financial institutions, and to keep markets open for trade and investment.That historic accord on a strategy for recovery was made possible in part by the policy actions already begun in China and the United States.China moved quickly as the crisis intensified with a very forceful program of investments and financial measures to strengthen domestic demand.These actions have been reinforced by similar actions in countries around the world. In contrast to the global crisis of the 1930s and to the major economic crises of the postwar period, the leaders of the world acted together. They acted quickly. Theytook steps to provide assistance to the most vulnerable economies, even as they faced exceptional financial needs at home. They worked to keep their markets open, rather than r etreating into self-defeating measures of discrimination and protect ion.China, despite your own manifest challenges a s a developing country, you are in an enviably strong position. But in most economies, the recession is still powerful and dangerous. Business and households in the United States, as in many countries, are still experiencing the most challenging economic and financial pressures in decades.These are necessary adjustments. They will entail a longer, slower process of recovery, with a very different pattern of future growth across countries than we have seen in the past several recoveries.Laying the Foundation for Future GrowthAs we address this immediate financial and economic crisis, it is important that we also lay the foundations for more balanced, sustained growth of the global economy once this recovery is firmly established.Although the United States and China start from very different positions, many of our domestic challenges are similar. In the United States, we are working to reform our health care system, to improve the quality of education, to rebuild our infrastructure, and to improve energy efficiency. These reforms are essential to boosting the productive capacity of our economy. These challenges are at the center of your reform priorities, too.In the United States, saving rates will have to increase, and the purchases of U.S. consumers cannot be as dominant a driver of growth as they have been in the past. In China, as your leadership has recognized, growth that is sustainable growth will require a very substantial shift from external to domestic demand, from an investment and export intensive driven growth, to growth led by consumption. Strengthening domestic demand will also strengthen Chinas ability to weather fluctuations in global supply and demand.In the United States, we are putting in place the foundations for restoring fiscal sustainability.The President also looks forward to working with Congress to further reduce our long-run fiscal deficit.The President has also proposed steps to encourage private saving, including through automatic enrollment in retirement savings accounts.。

国外贸易网站总汇

国外贸易网站总汇美国中央情报局CIA（Central intilligence angncy）：有各国整体报告。

网址：美国商业部国际贸易管理局（INTERNA TINAL TRADE ADMINISTRA TION）：有统计、国别报告等等。

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On the Economics of Peer-to-Peer Content Distribution Systems forLarge-volume ContentsSimon G.M.Koo†,Karthik Kannan‡,C.S.George Lee†,Sze-Wan Kwong‡†School of Electrical and Computer Engineering‡Krannert School of ManagementPurdue University,West Lafayette,IN47907Email:{koo,kkarthik,csglee,kwong}@AbstractPeer-to-Peer technology has changed the landscape of content sharing in the recent years.Among various content distribution systems,the key features of Bit-Torrent make it conducive to distributeﬁles with large volume,such as multimedia contents or scientiﬁc data. In this paper,we propose two major improvements on BitTorrent so that the social welfare in the peer-to-peer network is maximized.We present the peer grouping problem and provide an integer programming solution to the problem.The peers’individual behavior is also being studied,and we will present a cost-based incentive provisioning contribution mechanism to encourage sharing. Keywords:Peer-to-Peer Networks,BitTorrent,Con-tent Distribution Systems,Incentive Mechanism,and Network Economics.Introduction and MotivationSince theﬁrst introduction of Napster in1999,Peer-to-Peer(P2P)technology has changed the landscape of con-tent sharing.In the past few years,different P2P sharing tools like Gnutella,KazAa,eDonkey,WinMX,etc.have provided various functionalities and searching capabilities for P2Pﬁle sharing networks,and the technology itself has become very popular and mature.On the research front, emphasis have been put on the design of efﬁcient P2P sub-strates,which provide functionalities like low searching cost for locating content,ability to handleﬂashcrowd,etc. These designs have been proven to be effective when the cost(time)of looking up the desired content is a dominant factor.As a result,these substrates and technologies work ﬁne for distributing contents with relatively smaller sizes like MP3ﬁles or short video clips,and they are widely adopted.However,for large-volume contents like MPEG video on VCDs or DVDs,the searching cost compared to the actual distribution cost is relatively negligible,and the efﬁciency of the actual distribution process now becomes the critical performance metric for the system.Furthermore, these P2P applications are designed to enhance anonymity inﬁle sharing,thus they make the tracking about who has downloaded the content a very difﬁcult task.Even though P2P technology can provide a low-cost and scale-free solu-tion for content distribution,from the perspective of content providers who want to distribute large-volume contents to their customers,P2P may not be a desirable choice due to its inefﬁciency and lack of accounting ability,as they may want to restrict access only to subscribers or even charge for the contents one has downloaded.So,these content providers usually have to go for much more expensive solutions like CDN(Content Distribution Network).BitTorrent(BT)[1],since its release in2003,is one of the most popular P2P content distribution applications that has the potential to handle the above problem and serve as the agent for distribution of large-volume contents[2].The peer searching scheme that BT uses is a different one than most of the other P2P applications:For each content to be distributed,the content provider willﬁrst create a small.tor-rentﬁle(several KB),which contains information such as “tracker location”and digital signature of the content to be distributed.Clients will need toﬁrst download the.torrent ﬁle,and connect to the corresponding“tracker”.A tracker is a centralized entity,whose major function is to provide to the peers a list of other peers that are also download-ing the same content.Once the peers receive the list,they will establish connections and distribute the desired con-tents among themselves.The distribution process for BT is also different from the other popular P2P applications in the following:1.It uses the tracker to coordinate connections amongpeers.This removes the need ofﬂooding when a peerneeds to know who has the content.The tracker may also perform accounting and keep track on who has requested for and downloaded the content(not yet im-plemented in the current release).2.Each content(ﬁle or a collection ofﬁles)is dividedinto pieces and each piece is harshed into a20-bytes digital signature which is included in the.torrentﬁle.Clients can then verify the integrity of the pieces they have downloaded,and thus ensure the integrity of the whole content.3.Each peers will start helping the distribution processonce it has received at least one complete piece.They will concurrently upload the pieces they received to the others while they are still downloading the remaining pieces.Recent studies[3]have shown that by dividing the con-tent into pieces so that peers can start contributing once a complete piece is received,and the requirement for peers to upload while they download,have tremendous effect on increasing service capacity.These are the two major differ-ences that BT have over most P2P systems,and that trans-lates to more“effective servers”in the system,which means betterﬂashcrowd-handling ability and more efﬁcient con-tent distribution.The use of tracker could give the content provider an accounting medium and authentication mech-anism,although this has not been implemented in the cur-rent release.Most importantly,the distribution cost is cheap with respect to the content provider,since the process is as-sisted vastly by the clients.These features make BT an ex-cellent candidate for distribution of large-volume contents.However,with all the advantages mentioned above,we argue that the current design of BT is suboptimal in the fol-lowing sense:•When a peer contact the“tracker”,it will return a ran-dom list of peers that also want theﬁles.We conjecture that if the tracker does an intelligent“peer grouping”, the overall(social)utilities of the system will improve.•As documented in original paper of BT,the decision made by peers on which other peers to connect to fol-lows a simple“tit-for-tat”scheme,i.e.,a peer will up-load more to those who have uploaded more to itself.However,such incentives of sharing have only been barely studied,and there is a lack of systematic analy-sis to support the claim.•Peers are contributing their own resources in the pro-cess,so it is not reasonable to assume every peers will behave identically and rationally,and value their con-tribution of capacity the same way others do.In fact, it is more reasonable to assume peers are selﬁsh and only trying to maximize their own beneﬁts.As the content provider has no hard control over the clients’actions,we conjecture that through a game-theoretic analysis on peers behavior,and an optimistic op-timization of peers grouping at the tracker,we could vastly improve the performance of such low-cost content distribu-tion system.Problem DeﬁnitionWe envision the following problems:Peer Grouping Strategy What is the best“peer grouping”strategy so that the overall distribution process can be the most efﬁcient(Maximizing social welfare)?What is the overhead of such policy?Peers’behavior What are the peers’strategies for upload-ing to others and how to intelligently response to re-quests so that each peer will contribute what it is will-ing to and get what it deserves?(Reaching Pareto Ef-ﬁciency)From the content provider’s point of view,maximizing social utility means better utilization of rich,more willing-to-contribute peers to serve more contents,while penalize those who don’t contribute or contribute a small amount. The overall system performance,which can be measured in average downloading time,characterize the performance of the system.On the other hand,in a distributed environ-ment like P2P,there is no global control on the peers’be-havior.So each clients,when dealing with their neighbors, will need to play a non-cooperated game and maximize their own utilities.Peer Grouping StrategySince we have no knowledge about peers’exact behav-ior except assuming they are selﬁsh and try to maximize their own beneﬁt,there is no absolute optimal peer grouping scheme that can be done solely at the tracker.The perfor-mance of the overall system depends a lot on peers’actions. However,it is still possible to group peers with the most mu-tually disjoint collection of contents,so that we can assure in the worst case,a peer can still obtain the most number of pieces from its direct neighbors(with a“price”they agreed on)when the neighbors are not getting new content pieces from others.Analytically we considered the following:For aﬁxed number of peers N,we denote c i∈C,i=1,···N,where C is the set of content pieces,to be the subset of the pieces peer i has.We further denote s i∈S,i=1···N,where S is the set of all peers,be the set of neighbors peer i will connect to.We also assume that each peer i has a maximum out-degree d i,which is the maximum number it can connectto.In order to provide the maximum disjoint contents,we have the following optimization problem:max N i=1| j∈s i(c i\c j)|s.t.|s i|≤d i∀iHowever,the tracker will be heavily loaded if each peer periodically send a list of pieces it has to it.Under the cur-rent release,peers will send|c i|,which is the number of pieces peer i has,to the tracker.In order to approximate the utility function,without the need to change the current client applications,let X ij be a random variable represent-ing the number of pieces that peer j has but peer i doesn’t, and assume every piece of content is equally likely to ap-pear,then we can approximate the disjointness by Hyperge-ometric distribution:P(X ij=x)=(|C|−|c i|)C x×|ci|C(|cj|−x)|C|So we can approximate|c i\c j|by E[X ij].The union term in the utility function can then be approximated by: | j∈s i(c i\c j)|=(|C|−|c i|)× j∈s i|c j|。