中级微观经济学北京大学课件第一章.ppt

1、中级微观经济学Fall, 2004,介绍,结构,教员与助教 要求 教学大纲 例子: market for apartments,WHO AM I?,赵耀辉 北京大学中国经济研究中心 Office: 504 CCER Phone: 6275-4803 Email: Office Hours: Wednesdays 4:00-5:00pm,助教,廖志鹏, 张沈伟， 赵洪春 ， Office Hours: Tuesdays 4:00-5:00pm,教材,Intermediate Microeconomics: A Modern Approach (Sixth Edition) by Hal R. V

2、arian W. W. Norton， 2003,作业,几乎每次课后都有作业 周一的作业在周四课前交 周四的作业在周一课前交 课后领回作业 不交或迟交作业将不得分,考试,两次测验，一次期中，一次期末 注意考试日期 测验和期中考试只考阶段内容 期末考试将考全部课程内容 除极特殊情况以外，缺考者得零分 没有补考或者缓考,成绩,家庭作业: 20 测验: 20 期中考试: 20 期末考试: 40,The Theory of Economics does notfurnish a body of settled conclusionsimmediately applicable to policy. I

3、t isa method rather than a doctrine, anapparatus of the mind, a technique ofthinking which helps its possessor todraw correct conclusions- John Maynard Keynes,Is Economics Useful?,Becoming a thinker Changes the way you view life and understand problems An all round major,Economics Graduates,Jobs for

4、 Economists,Business economists Government economists Academic economists,Microeconomics,Theory Applications Labor economics Economics of education Development economics Agricultural economics Industrial organizations Health economics ,Course Outline,Consumer theory (1-15) Producer theory (18-27) Ma

5、rket equilibrium (16-17, 30-32) Special topics on equilibrium,Economic Modeling,What causes what in economic systems? Which variables are determined outside the model (exogenous) Which variables are to be determined by the model (endogenous) At what level of detail shall we model an economic phenome

6、non?,Modeling the Apartment Market,Central question: How are apartment rents determined? Suppose (simplifying assumptions) apartments are close or distant, but otherwise identical distant apartments rents are exogenous and known many potential renters and landlords, i.e., competitive market,A Normat

7、ive Question,Will the allocation of apartments be desirable? Need to know: Who will rent close apartments? At what price?,Two Principles in Economics,Optimization: Each person tries to choose the best alternative available to him or her. Equilibrium: Market price adjusts until quantity demanded equa

8、ls quantity supplied.,Modeling Individual Demand,Discrete commodity: 0 or 1 unit Choose either distant or close apartment Close apartments are more desirable but more expensive Tend to choose close apartment if Distant apartments are also expensive. Higher income. Decide: The maximum rent you are wi

9、lling to pay for a close apartment.,Modeling Market Demand,Demand: Suppose the most any one person is willing to pay to rent a close apartment is $500/month. Thenp = $500 QD = 1. Suppose the price has to drop to $490 before a 2nd person would rent. Thenp = $490 QD = 2.,Modeling Apartment Demand,The

10、lower is the rental rate p, the larger is the quantity of close apartments demandedp QD . The quantity demanded vs. price graph is the market demand curve for close apartments.,Market Demand Curve for Apartments,p,QD,Modeling Apartment Supply,Supply: It takes time to build more close apartments so i

11、n this short-run the quantity available is fixed (at say 100).,Market Supply Curve for Apartments,p,QS,100,Competitive Market Equilibrium,“low” rental price quantity demanded of close apartments exceeds quantity available price will rise. “high” rental price quantity demanded less than quantity avai

12、lable price will fall.,Competitive Market Equilibrium,Quantity demanded = quantity available price will neither rise nor fall so the market is at a competitive equilibrium.,Competitive Market Equilibrium,p,QD,QS,100,Competitive Market Equilibrium,p,QD,QS,pe,100,Competitive Market Equilibrium,p,QD,QS

13、,pe,100,People willing to pay pe for close apartments get close apartments.,Competitive Market Equilibrium,p,QD,QS,pe,100,People willing to pay pe for close apartments get close apartments.,People not willing to pay pe for close apartments get distant apartments.,Competitive Market Equilibrium,Q: Wh

14、o rents the close apartments? A: Those most willing to pay. Q: Who rents the distant apartments? A: Those least willing to pay. So the competitive market allocation is by “willingness-to-pay”.,Comparative Statics,What is exogenous in the model? price of distant apartments quantity of close apartment

15、s incomes of potential renters. What happens if these exogenous variables change?,Comparative Statics,Suppose the price of distant apartment rises. Demand for close apartments increases (rightward shift), causing a higher price for close apartments.,Market Equilibrium,p,QD,QS,pe,100,Market Equilibri

16、um,p,QD,QS,pe,100,Higher demand,Market Equilibrium,p,QD,QS,pe,100,Higher demand causes highermarket price; same quantitytraded.,Comparative Statics,Suppose there were more close apartments. Supply is greater, so the price for close apartments falls.,Market Equilibrium,p,QD,QS,pe,100,Market Equilibri

17、um,p,QD,QS,100,Higher supply,pe,Market Equilibrium,p,QD,QS,pe,100,Higher supply causes alower market price and alarger quantity traded.,Comparative Statics,Suppose potential renters incomes rise, increasing their willingness-to-pay for close apartments. Demand rises (upward shift), causing higher pr

18、ice for close apartments.,Market Equilibrium,p,QD,QS,pe,100,Market Equilibrium,p,QD,QS,pe,100,Higher incomes causehigher willingness-to-pay,Market Equilibrium,p,QD,QS,pe,100,Higher incomes causehigher willingness-to-pay,higher market price, andthe same quantity traded.,Imperfectly Competitive Market

19、s,Amongst many possibilities are: a monopolistic landlord a perfectly discriminatory monopolistic landlord a competitive market subject to rent control.,A Monopolistic Landlord,When the landlord sets a rental price p he rents D(p) apartments. Revenue = pD(p). Revenue is low if p 0 Revenue is low if

20、p is so high that D(p) 0. An intermediate value for p maximizes revenue.,Monopolistic Market Equilibrium,p,QD,Lowprice,Low price, high quantitydemanded, low revenue.,Monopolistic Market Equilibrium,p,QD,Highprice,High price, low quantitydemanded, low revenue.,Monopolistic Market Equilibrium,p,QD,Mid

21、dleprice,Middle price, medium quantitydemanded, larger revenue.,Monopolistic Market Equilibrium,p,QD,QS,Middleprice,Middle price, medium quantitydemanded, larger revenue.Monopolist does not rent all theclose apartments.,100,Monopolistic Market Equilibrium,p,QD,QS,Middleprice,Middle price, medium qua

22、ntitydemanded, larger revenue.Monopolist does not rent all theclose apartments.,100,Vacant close apartments.,Perfectly Discriminatory Monopolistic Landlord,Imagine the monopolist knew everyones willingness-to-pay. Charge $500 to the most willing-to-pay, charge $490 to the 2nd most willing-to-pay, et

23、c.,Discriminatory Monopolistic Market Equilibrium,p,QD,QS,100,p1 =$500,1,Discriminatory Monopolistic Market Equilibrium,p,QD,QS,100,p1 =$500,p2 =$490,1,2,Discriminatory Monopolistic Market Equilibrium,p,QD,QS,100,p1 =$500,p2 =$490,1,2,p3 =$475,3,Discriminatory Monopolistic Market Equilibrium,p,QD,QS

24、,100,p1 =$500,p2 =$490,1,2,p3 =$475,3,Discriminatory Monopolistic Market Equilibrium,p,QD,QS,100,p1 =$500,p2 =$490,1,2,p3 =$475,3,pe,Discriminatory monopolistcharges the competitive marketprice to the last renter, andrents the competitive quantityof close apartments.,Rent Control,Local government im

25、poses a maximum legal price, pmax pe, the competitive price.,Market Equilibrium,p,QD,QS,pe,100,Market Equilibrium,p,QD,QS,pe,100,pmax,Market Equilibrium,p,QD,QS,pe,100,pmax,Excess demand,Market Equilibrium,p,QD,QS,pe,100,pmax,Excess demand,The 100 close apartments are no longer allocated bywillingne

26、ss-to-pay (lottery, lines,large families first?).,Which Market Outcomes Are Desirable?,Which is better? Rent control Perfect competition Monopoly Discriminatory monopoly,Pareto Efficiency,Vilfredo Pareto; 1848-1923. A Pareto outcome allows no “wasted welfare”; i.e. the only way one persons welfare c

27、an be improved is to lower another persons welfare.,Pareto Efficiency,Jill has an apartment; Jack does not. Jill values the apartment at $200; Jack would pay $400 for it. Jill could sublet the apartment to Jack for $300. Both gain, so it was Pareto inefficient for Jill to have the apartment.,Criteri

28、on for Pareto Efficiency,A Pareto inefficient outcome means there remain unrealized mutual gains-to-trade. Any market outcome that achieves all possible gains-to-trade must be Pareto efficient.,Pareto Efficiency,Competitive equilibrium: all close apartment renters value them at the market price pe or more all others value close apartments at less than pe so no mutually beneficial trades remain so the outcome is Pareto efficient.,Pareto Efficiency,Discriminatory Monopoly: