ChAsymmetricInformation(中级微观经济学清华大学,钟笑寒)精讲
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Ch03Preferences(中级微观经济学-清华大学,钟笑寒)
Take-home Question
Peter
prefer apple to orange, orange to banana, and banana to apple. (So he is a non-transitive man.) He would like offer 1 dollar to exchange an orange for an apple, a banana for orange, an apple for a banana. What would happen then? Do you think Peter is rational?
Preference Relation
From
, we can derive two other important relations: – strict preference, : x y x y but not y x Read as “x is more preferred than is y”. – Indifference, : x y x y and y x Read as “x is exactly as preferred as is y”.
9
5 5 9
x1
Preferences Exhibiting Satiation
A
bundle strictly preferred to any other is a satiation point or a bliss point. What do indifference curves look like for preferences exhibiting satiation?
x1
Indifference Curves
清华大学中级微观经济学讲义(清华 李稻葵)7
The Strong Axiom of Revealed Preference
A: ($1,$3,$10) (3,1,4). B: ($4,$3,$6) (2,5,3). C: ($1,$1,$5) (4,4,3).
Choice Prices A B C A $46 $39 $24 B $47 $41 $22 C $46 $46 $23
Digression: Science vs. Engineering (对比科学家思维与工程师思维） 找问题与解问题的不同 –要对问题提问题 要对问题提问题 务虚与务实的不同 解释世界与改造世界的不同 –旁观者与参与者的不同 旁观者与参与者的不同
Maintained Assumptions on Preferences
The Strong Axiom of Revealed Preference
Consider the following data: A: (p1,p2,p3) = (1,3,10) & (x1,x2,x3) = (3,1,4) B: (p1,p2,p3) = (4,3,6) & (x1,x2,x3) = (2,5,3) C: (p1,p2,p3) = (1,1,5) & (x1,x2,x3) = (4,4,3)
Recovering Indifference Curves
Suppose we observe: A: (p1,p2) = ($1,$1) & (x1,x2) = (15,15) B: (p1,p2) = ($2,$1) & (x1,x2) = (10,20) C: (p1,p2) = ($1,$2) & (x1,x2) = (20,10) D: (p1,p2) = ($2,$5) & (x1,x2) = (30,12) E: (p1,p2) = ($5,$2) & (x1,x2) = (12,30). Where lies the indifference curve containing the bundle A = (15,15)?
清华大学中级微观经济学讲义清华李稻葵15-文档资料26页
Marginal Revenue and Own-Price Elasticity of Demand
p
a
p (q )ab q
a/2b
a/b q
M R (q ) a 2 b q
Marginal Revenue and Own-Price p Elasticity of Demand
a
M R (q ) a 2 b q
Then Xi = (a-pi)/b and
dX
* i
1.
Therefore,
dpi b
X i * ,p i (a p p ii)/b b 1 a p ip i.
Point Own-Price Elasticity
pi
pi = a - bXi*
X j(p 1 ,p 2 ,m 1 , ,m n ) n x * ji(p 1 ,p 2 ,m i).
i 1
From Individual to Market Demand
Functions
p1
p1
p1’
p1’
p1”
p1”
p1
20
x
* 1
A
15
x
* 1
B
p1’
The “horizontal sum”
The elasticity of variable X with
respect to variable Y is
x,y
%x. %y
Slope Vs. Elasticity
Q: Why not just use the slope of a demand curve to measure the sensitivity of quantity demanded to a change in a commodity’s own price?
Ch12Uncertainty(中级微观经济学-清华大学,钟笑寒)
m L Cna Ca 1 1
slope
mL
1
Where is the most preferred state-contingent consumption plan?
m L Ca
Preferences Under Uncertainty
In
general, how a person values consumption in one state as compared to another will depend on the probability that the state in question will actually occur. Suppose that we are considering two mutually exclusive states. Let c1 and c2 represent consumption in state 1 and 2, and let 1 and 2 be the probabilities that state 1 or 2 actually occurs. Thus 1+2=1. The utility function can be written as U(c1,c2,1,2)
State-Contingent Budget Constraints
m L 1
Cna
m L Cna Ca 1 1
m
The endowment bundle.
mL
m L Ca
State-Contingent Budget Constraints
m L 1
State-Contingent Budget Constraints
清华大学中级微观经济学讲义(清华 李稻葵)30
The Endowment Allocation
2 OB 2 6 4 OA 6 8
ω = (2,2)
B
The Endowment Allocation
2 OB 2 6 4 OA 6 8 The endowment allocation
A ω = (6,4) B
ω = (2,2)
The Endowment Allocation
/ Remarks on the Final
Final Examination: 1. Final exam is comprehensive. 2. It mainly covers the material after midterm. 3. The materials before midterm are important in two ways: 1) some problems may directly come from those chapters. 2) the materials before midterm provide a foundation for new materials. The format of the final will be the same as that in the midterm. Office Hour: 4-5 pm Thursday
Starting an Edgeworth Box
Height = A B ω2 + ω2
= 4+ 2 =6
The dimensions of the box are the quantities available of the goods.
A B ω1 + ω1 = 6 + 2 = 8 Width =
清华经管钟笑寒副教授介绍
清华经管钟笑寒副教授介绍清华经管钟笑寒副教授介绍钟笑寒经济系副教授办公室伟伦楼551个人简介研究成果研究项目钟笑寒，清华大学经济管理学院经济系副主任，副教授。
1994年获清华大学经济管理学院管理信息系统专业工学学士学位，1999年获清华大学经济管理学院数量经济学专业经济学博士学位。
主要讲授课程包括：经济学原理，博弈论，政治经济学。
钟老师的研究领域包括发展经济学，劳动经济学，政治经济学，应用微观经济学，中国经济。
主持过多个重点科研项目，在《经济学季刊》《数量经济技术经济研究》《经济学报》和《中国证券报》等多种刊物和报纸上上发表过二十多篇学术论文。
出版过《文物保护与旅游业发展：一个经济学的分析》《中国农民故事》等著作，并翻“GradualReformorRadicalReform:Sustainable View”,The4thAnnualInternationalConferenceo nTransitionEconomics,Beijing,No.D08.发表论文白重恩、王鑫、钟笑寒，“出口退税政策调整对中国出口影响的实证分析”，《经济学季刊》，第10卷第3期。
乔雪，钟笑寒，“经济发展、危险行为与艾滋病传播”，《南方经济》，2011年第5期。
钟笑寒，“死亡率与产量负相关：煤炭行业‘关井’政策效应分析”，《经济学报》，第5辑。
钟笑寒，“城乡移民与收入不平等：基于基尼系数的理论分析”，《数量经济技术经济研究》，2008年第8期。
冯俊新、张凯云、钟笑寒，“文化遗产资源与区域旅游业发展”，《经济地理》，2008年第3期。
程子建、钟笑寒：“文物保护与旅游产业化：不完全合同理论”，《旅游学刊》，2007年第6期。
钟笑寒，“劳动力流动与工资不平等”，《中国社会科学》，2006年第1期。
钟笑寒，“不确定性、信息与权力：非常规事件下的中央和地方关系”，《经济学报》，第1卷第2辑，2005年12月。
孙睿君，钟笑寒，“运用旅行费用模型估计典型消费者的旅游需求及其收益：对中国的实证研究”，《统计研究》，2005年第12期（总第170期）。
Ch05Choice(中级微观经济学-清华大学,钟笑寒)
x* 20
y * x1 p1
x1
Examples of Corner Solutions -the Perfect Substitutes Case
So when U(x1,x2) = x1 + x2, the most preferred affordable bundle is (x1*,x2*) where y * * ( x1 , x 2 ) ,0 if p1 < p2 p1 and
y p1
x1
Examples of Corner Solutions -the Perfect Substitutes Case
a1 b dx 2 U/ x1 ax1 x 2 ax 2 MRS . a b 1 dx1 U/ x 2 bx1 bx1 x 2
Computing Ordinary Demands a Cobb-Douglas Example.
So
the MRS is
a1 b dx 2 U/ x1 ax1 x 2 ax 2 MRS . a b 1 dx1 U/ x 2 bx1 bx1 x 2
At
(x1*,x2*), MRS = -p1/p2 so
ax* 2
* bp1 * x2 x1 . ap2
p1 * p2 bx1
(A)
Computing Ordinary Demands a Cobb-Douglas Example.
(x1*,x2*)
also exhausts the budget so
This simplifies to ….
(A) (B)
bp1 * * p1x1 p2 x1 m. ap2
y * x1 p1
x1
Examples of Corner Solutions -the Perfect Substitutes Case
So when U(x1,x2) = x1 + x2, the most preferred affordable bundle is (x1*,x2*) where y * * ( x1 , x 2 ) ,0 if p1 < p2 p1 and
y p1
x1
Examples of Corner Solutions -the Perfect Substitutes Case
a1 b dx 2 U/ x1 ax1 x 2 ax 2 MRS . a b 1 dx1 U/ x 2 bx1 bx1 x 2
Computing Ordinary Demands a Cobb-Douglas Example.
So
the MRS is
a1 b dx 2 U/ x1 ax1 x 2 ax 2 MRS . a b 1 dx1 U/ x 2 bx1 bx1 x 2
At
(x1*,x2*), MRS = -p1/p2 so
ax* 2
* bp1 * x2 x1 . ap2
p1 * p2 bx1
(A)
Computing Ordinary Demands a Cobb-Douglas Example.
(x1*,x2*)
also exhausts the budget so
This simplifies to ….
(A) (B)
bp1 * * p1x1 p2 x1 m. ap2
清华大学李稻葵中级微观经济学讲义
Chapter One
The Market --- Appreciating Economic Modeling
The Purpose of this Chapter
• To begin to understand the art of building an economic model • To begin to understand three basic elements of modeling in economics:
– apartments are close or distant, but otherwise identical – distant apartments rents are exo genous (外生变量） and known – many potential renters and landlords
– Purpose – Simplification through assumptions – Value judgment
The Purpose of an Economic Model
• The purpose of an economic model is to help provide precise insights (精确的 洞察力）on a specific economic phenomenon. • Thus:
– Different phenomena needs different model; – Simplification by assumption is necessary
An Illustration: Modeling the Apartment Market
• Purpose: How are apartment rents determined? Are rents “desirable”? • Simplifying assumptions:
The Market --- Appreciating Economic Modeling
The Purpose of this Chapter
• To begin to understand the art of building an economic model • To begin to understand three basic elements of modeling in economics:
– apartments are close or distant, but otherwise identical – distant apartments rents are exo genous (外生变量） and known – many potential renters and landlords
– Purpose – Simplification through assumptions – Value judgment
The Purpose of an Economic Model
• The purpose of an economic model is to help provide precise insights (精确的 洞察力）on a specific economic phenomenon. • Thus:
– Different phenomena needs different model; – Simplification by assumption is necessary
An Illustration: Modeling the Apartment Market
• Purpose: How are apartment rents determined? Are rents “desirable”? • Simplifying assumptions:
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EV $1200*(1/ 2) $2400(1/ 2) $1800.
Adverse Selection
But
a peach seller cannot negotiate a price below $2000 and will exit the market. So all buyers know that remaining sellers own lemons only. Buyers will pay at most $1200 and only lemons are sold.
Adverse Selection
Hence
the lemons “crowd out” the peaches from the market. Gains-to-trade are reduced since no peaches are traded. The presence of the lemons inflicts an external cost on peach owners. We say adverse selection arises when only owners of relatively bad goods are willing to accept a buyer’s offer at any given price.
*Take-home Question
In
what ways can asymmetric information affect the functioning of a market? Four applications will be considered: adverse selection moral hazard signaling incentives contracting.
Asymmetric Information in Markets
Imperfectly
informed markets with one side better informed than the other are markets with asymmetric information.
Asymmetric Information in Markets
Adverse Selection
Suppose
no buyer can tell a peach from a lemon before buying. What is the most a buyer will pay for any car?
Aection
If
every buyer can tell a peach from a lemon, then lemons sell for between $1,000 and $1,200, and peaches sell for between $2,000 and $2,400. Gains-to-trade are generated when buyers are well informed.
Asymmetric Information in Markets
A
doctor knows more about medical services than does the buyer. An insurance buyer knows more about his riskiness than does the seller. A used car’s owner knows more about it than does a potential buyer.
Chapter Thirty-Six
Asymmetric Information
Information in Competitive Markets
In
purely competitive markets all agents are fully informed about traded commodities and other aspects of the market. What about markets for medical services, or insurance, or used cars?
Adverse Selection
Consider
a used car market. 100 people want to sell their used cars and 100 want to buy a used car. Everyone knows 50 of the cars are “lemons” and 50 are “peaches”. The current owner of each car knows its quality, but the prospective buyers don’t know and given car’s quality. Each lemon seller will accept $1,000; a buyer will pay at most $1,200. Each peach seller will accept $2,000; a buyer will pay at most $2,400.
this case, the buyers have to guess about how much each car is worth. Since a car is equally likely to be a peach as a lemon, then a buyer would be willing to pay the expected value of the car, i.e,