01_The_Market.ppt

1、MicroeconomicsHal R.Varian,Chapter One,The Market,The Theory of Economics does not furnish a body of settled conclusions immediately applicable to policy. It is a method rather than a doctrine, an apparatus of the mind, a technique of thinking which helps its possessor to draw correct conclusions -

2、John Maynard Keynes,经济学只是一种方法和工具，而不是金科玉律 - 约翰梅纳德凯恩斯,Economic Modeling经济模型,What causes what in economic systems?经济系统里各因素的因果关系如何？ At what level of detail shall we model an economic phenomenon?我们应在多大细节程度上对经济现象进行建模？ Which variables are determined outside the model (exogenous) and which are to be determi

3、ned by the model (endogenous)?哪些因素是外生变量，哪些变量是内生变量?,Modeling the Apartment Market对公寓租赁市场建模,How are apartment rents determined?公寓租金是怎么决定的？ Suppose假设 apartments are close or distant, but otherwise identical公寓只有远近之分，其它方面都一样 distant apartments rents are exogenous and known远的公寓的租金是外生和已知的 many potential re

4、nters and landlords有很多潜在的承租人和出租人,Modeling the Apartment Market对公寓租赁市场建模,Who will rent close apartments?谁会租靠近的公寓？ At what price?在什么价格水平下？ Will the allocation of apartments be desirable in any sense?在任何意义上讲，对于公寓的分配是否有必要? How can we construct an insightful model to answer these questions?我们应该怎样来建立正确的模型

5、来回答这些问题?,Economic Modeling Assumptions经济模型的假设,Two basic postulates:两个基本假定 Rational Choice: Each person tries to choose the best alternative available to him or her. 理性选择: 人们总是选择他们能支付得起的最佳消费方式 Equilibrium: Market price adjusts until quantity demanded equals quantity supplied. 均衡: 价格会自行调整，直到人们的需求数量与供给

6、数量相等,Modeling Apartment Demand对公寓需求建模,Demand: Suppose there is one person who is willing to pay to rent a close apartment is $500/month. Then p = $500 QD = 1. 需求: 如果只有一个人愿意每月付500美元租一套房. 那么p = $500 QD = 1. Suppose the price has to drop to $490 before a 2nd person would rent. Then p = $490 QD = 2. 假设人

7、们愿意支付的第二高的价格是490美元. 那么p = $490 QD = 2.,Modeling Apartment Demand对公寓需求建模,The lower is the rental rate p, the larger is the quantity of close apartments demandedp QD . 租房价格p越低，对于较近的公寓的需求量就会上升，也即p QD . The quantity demanded vs. price graph is the market demand curve for close apartments. 把需求量和市场价格联系起来的

8、曲线就是较近的公寓的市场需求曲线.,Market Demand Curve for Apartments对于公寓的市场需求曲线,p,QD,Modeling Apartment Supply对公寓供给建模,Supply: It takes time to build more close apartments so in this short-run the quantity available is fixed (at say 100). 供给: 因为建更多的较近的公寓需要时间，所以短期来说，供给是固定的（比如是100）.,Market Supply Curve for Apartments公

9、寓的市场供给曲线,p,QS,S,Competitive Market Equilibrium竞争市场均衡,“low” rental price quantity demanded of close apartments exceeds quantity available price will rise. 低的租赁价格 靠近学校的公寓的需求量超过现货数量 价格上涨. “high” rental price quantity demanded less than quantity available price will fall. 高的租赁价格 需求量小于现货数量 价格下降.,Competit

10、ive Market Equilibrium竞争性市场均衡,Quantity demanded = quantity available price will neither rise nor fall 需求量 = 现货数量 价格既不升也不降 so the market is at a competitive equilibrium. 因此市场处于竞争性均衡状态.,Competitive Market Equilibrium竞争性市场均衡,p,QD,QS,100,Competitive Market Equilibrium竞争性市场均衡,p,QD,QS,pe,100,Competitive M

11、arket Equilibrium竞争性市场均衡,p,QD,QS,pe,100,People willing to pay pe for close apartments get close apartments. 愿意支付pe 的价格的人租赁靠近学校的公寓.,Competitive Market Equilibrium竞争性市场均衡,p,QD,QS,pe,100,People willing to pay pe for close apartments get close apartments. 愿意支付pe 的价格的人租赁靠近学校的公寓.,People who are not willin

12、g to pay pe for close apartments get close apartments.不愿意支付价格pe的人租赁距离学校较远的公寓.,Competitive Market Equilibrium竞争性市场均衡,Q: Who rents the close apartments?问: 谁租赁靠近学校的公寓? A: Those most willing to pay.答: 那些最愿意支付租金的人. Q: Who rents the distant apartments?问: 谁租赁距离学校较远的公寓? A: Those least willing to pay.答: 那些最不

13、愿意支付租金的人. So the competitive market allocation is by “willingness-to-pay”.因此完全竞争市场是通过支付意愿来分配公寓的.,Comparative Statics比较静态分析,What is exogenous in the model? price of distant apartments quantity of close apartments incomes of potential renters. 模型中什么是外生变量? 距离学校较远的公寓租金价格 靠近学校公寓的数量 潜在承租人的收入. What happens

14、 if these exogenous variables change?如果这些外生变量改变会有什么结果?,Comparative Statics比较静态分析,Suppose the price of distant apartment rises.假设距离学校较远的公寓租金价格上涨. Demand for close apartments increases (rightward shift 右移), causing a higher price for close apartments. 对于靠近学校公寓的租赁需求会上升，导致靠近学校的公寓的租金价格上升.,Market Equilibr

15、ium市场均衡,p,QD,QS,pe,100,Market Equilibrium市场均衡,p,QD,QS,pe,100,Higher demand需求上升,Market Equilibrium市场均衡,p,QD,QS,pe,100,Higher demand causes highermarket price; same quantitytraded.需求上升导致市场价格上升， 但成交量不变.,Comparative Statics比较静态分析,Suppose there were more close apartments.假设有更多的较为靠近学校的公寓. Supply is greate

16、r, so the price for close apartments falls.供给增加, 那么 靠近学校的公寓的价格会下降.,Market Equilibrium市场均衡,p,QD,QS,pe,100,市场均衡,p,QD,QS,100,Higher supply供给增加,pe,市场均衡,p,QD,QS,pe,100,Higher supply causes alower market price and alarger quantity traded. 供给增加导致更低的市场 价格和更高的交易量.,Comparative Statics比较静态分析,Suppose potential

17、renters incomes rise, increasing their willingness-to-pay for close apartments.假设潜在的租赁人的收入增加, 他们更加意愿租靠近学校的公寓. Demand rises (upward shift 上移), causing higher price for close apartments. 需求上升 (向上移动), 导致靠近学校的公寓的租赁价格上升.,Market Equilibrium市场均衡,p,QD,QS,pe,100,市场均衡,p,QD,QS,pe,100,Higher incomes cause highe

18、r willingness-to-pay更高的收入导致租赁人更加愿意租靠近学校的公寓,市场均衡,p,QD,QS,pe,100,Higher incomes cause higher willingness-to-pay,higher market price, andthe same quantity traded.更高的收入导致租赁人更加愿意租靠近学校的公寓,更高的市场价格和相同的交易量.,Taxation Policy Analysis税收政策分析,Local government taxes apartment owners. 地方政府对公寓出租人征税. What happens to

19、price？价格如何变化？ quantity of close apartments rented?靠近学校的公寓的出租数量如何变化? Is any of the tax “passed” to renters?政府所征税款是否回转移给租赁人?,Taxation Policy Analysis税收政策分析,Market supply is unaffected.市场供给不受影响. Market demand is unaffected.市场需求不受影响. So the competitive market equilibrium is unaffected by the tax.因此竞争性市场

20、均衡不受税收影响. Price and the quantity of close apartments rented are not changed.价格和靠近学校的公寓的出租量也不会改变. Landlords pay all of the tax.出租人支付所有税款.,Imperfectly Competitive Markets不完全竞争市场,Amongst many possibilities are:可能情况包括: a monopolistic landlord一个垄断的出租人 a perfectly discriminatory monopolistic landlord一个完全歧

21、视性的垄断出租人 a competitive market subject to rent control.一个受到租金影响的竞争性市场.,A Monopolistic Landlord一个垄断出租人,When the landlord sets a rental price p he rents D(p) apartments.当出租人把租金价格设为p时，他能租出 D(p)套公寓. Revenue = pD(p).收益= pD(p). Revenue is low if p 0.当p 0时收益很低 Revenue is low if p is so high that D(p) 0.当p很高

22、时，由于 D(p) 0，收益也很低 An intermediate value for p maximizes revenue.一个居中的价格能够最大化出租人收益.,Monopolistic Market Equilibrium垄断市场均衡,p,QD,Lowprice 低价,Low price, high quantity demanded, low revenue.低价, 高需求量, 低收益,垄断市场均衡,p,QD,Highprice 高价,High price, low quantitydemanded, low revenue.高价,低需求量，低收益.,垄断市场均衡,p,QD,Middl

23、eprice 中间 价格,Middle price, medium quantitydemanded, larger revenue. 中间价格, 中等数量需求, 更高收益,垄断市场效率,p,QD,QS,Middleprice 中间 价格,Middle price, medium quantity demanded, larger revenue. Monopolist does not rent all the close apartments.中间价格，中间数量需求，更高的收入。垄断厂商并不出租所有的公寓,100,垄断市场均衡,p,QD,QS,Middleprice 中间 价格,Middl

24、e price, medium quantity demanded, larger revenue. Monopolist does not rent all the close apartments.中间价格，中间数量需求，更高的收入。垄断厂商并不出租所有的公寓,100,Vacant close apartments 靠近学校的空置公寓.,Perfectly Discriminatory Monopolistic Landlord完全歧视垄断出租人,Imagine the monopolist knew everyones willingness-to-pay.假设垄断出租人知道每一个人的租

25、赁公寓的意愿. Charge $500 to the most willing-to-pay,对最想租公寓的承租人收取$500的出租费 charge $490 to the 2nd most willing-to-pay, etc.对第二愿意租公寓的人收取 $490租金, 等等.,Discriminatory Monopolistic Market Equilibrium有歧视的垄断市场均衡,p,QD,QS,100,p1 =$500,1,Discriminatory Monopolistic Market Equilibrium有歧视的垄断市场均衡,p,QD,QS,100,p1 =$500,p

26、2 =$490,1,2,Discriminatory Monopolistic Market Equilibrium有歧视的垄断市场均衡,p,QD,QS,100,p1 =$500,p2 =$490,1,2,p3 =$475,3,Discriminatory Monopolistic Market Equilibrium有歧视的垄断市场均衡,p,QD,QS,100,p1 =$500,p2 =$490,1,2,p3 =$475,3,Discriminatory Monopolistic Market Equilibrium有歧视的垄断市场均衡,p,QD,QS,100,p1 =$500,p2 =$4

27、90,1,2,p3 =$475,3,pe,Discriminatory monopolistcharges the competitive marketprice to the last renter, andrents the competitive quantityof close apartments. 有歧视的垄断出租人对最后一个 承租人收取市场为竞争性市场时的 交易价格, 并且出租当市场为竞争 性市场时的公寓出租量.,Rent Control租赁控制,Local government imposes a maximum legal price, pmax pe, the compet

28、itive price. 地方政府设定一个最高出租价格, pmax pe,竞争性市场价格.,Market Equilibrium市场均衡,p,QD,QS,pe,100,Market Equilibrium市场均衡,p,QD,QS,pe,100,pmax,Market Equilibrium市场均衡,p,QD,QS,pe,100,pmax,Excess demand额外需求,市场均衡,p,QD,QS,pe,100,pmax,Excess demand过度需求,The 100 close apartments are no longer allocated by willingness-to-pa

29、y (lottery, lines, large families first?). 100套靠近学校的公寓不在依据承租人的意愿来分配 (律师,大家庭优先?).,Which Market Outcomes Are Desirable?哪个市场的结果是可取的,Which is better? Rent control Perfect competition Monopoly Discriminatory monopoly 哪个更好哦? 租赁控制 完全竞争市场 垄断 歧视性垄断,Pareto Efficiency帕累托效率,Vilfredo Pareto; 1848-1923. 维尔弗雷多帕累托

30、; 1848-1923. A Pareto outcome allows no “wasted welfare”;帕雷托结果不允许存在福利的浪费 ; i.e. the only way one persons welfare can be improved is to lower another persons welfare. 唯一能改善一个人福利的方法是降低其他人的福利.,Pareto Efficiency帕累托效率,Jill has an apartment; Jack does not.吉尔有一套公寓; 杰克没有. Jill values the apartment at $200;

31、Jack would pay $400 for it.吉尔为了租一套公寓愿意支付$200，但杰克愿意支付$400. Jill could sublet the apartment to Jack for $300.吉尔可以以$300的价格转租给杰克. Both gain, so it was Pareto inefficient for Jill to have the apartment.同样, 因此对于吉尔来说是帕累托无效的.,Pareto Efficiency帕累托效率,A Pareto inefficient outcome means there remain unrealized

32、mutual gains-to-trade.帕累托无效意味着存在没有实现的互惠交易. Any market outcome that achieves all possible gains-to-trade must be Pareto efficient.任何完成了所有可能互惠交易的市场都是帕累托有效的.,Pareto Efficiency帕累托效率,Competitive equilibrium:竞争均衡: all close apartment renters value them at the market price pe or more所有承租人对于靠近学校的公寓的租金估价为市场价pe或者更高 all others value close apartments at less than pe所有其他人对于靠近学校公寓的租金估价至少为 pe so no mutually beneficial trades remain因此没有相互互惠的交易产生 so the outcome is Pareto efficient. 因此结果是帕累托有效的.,Pareto Efficiency帕累托