LECTURE5竞争性市场与一般均衡(平狄克,微观经济学-厦hhs.pptx

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1、微观经济学(平狄克，鲁宾费尔德，第四版)LECTURE 5 竞争性市场与一般均衡 1一、竞争性市场 2完全竞争市场完全竞争市场 n完全竞争市场的条件：n价格接受者：单个厂商产出占市场总供给的很小份额，因此无法影响市场价格；单个消费者购买的产品占市场需求的很小份额，因此无法影响市场价格。n产品同质性：所有厂商的产品是完全可替代的。n自由进出入：买方可无成本地从一个厂商转向另一个厂商；厂商可无成本进入退出某个产业。3财富效应n消费者剩余和厂商剩余：n在一个竞争性市场中的各自份额，PP5；n政府政策的财富效应：n因政府干预市场而导致的收益或损失，通过消费者剩余和厂商剩余的增减得到衡量。n政府制定价格

2、高限，产生无谓损失。PP6当消费者的需求具有足够低的弹性时，政府限价在降低厂商剩余的同时，还可能给消费者带来消费者剩余的绝对下降。PP7n政府制定价格低限，同样产生无谓损失。PP8 4ProducerSurplusBetween 0 and Q0 producers receive a net gain from selling each product-producer surplus.ConsumerSurplusConsumer and Producer SurplusQuantity0PriceSD5Q0Consumer C107Consumer BConsumer ABetween

3、0 and Q0 consumers A and Breceive a net gain from buying the product-consumer surplus5The loss to producers isthe sum of rectangleA and triangle C.TriangleB and C together measurethe deadweight loss.BACThe gain to consumers isthe difference betweenthe rectangle A and thetriangle B.Deadweight LossCha

4、nge in Consumer andProducer Surplus from Price ControlsQuantityPriceSDP0Q0PmaxQ1Q2Suppose the governmentimposes a price ceiling Pmaxwhich is below the market-clearing price P0.6BAPmaxCQ1If demand is sufficientlyinelastic,triangle B can be larger than rectangleA and the consumer suffers a net loss fr

5、omprice controls.ExampleOil price controlsand gasoline shortagesin 1979SDEffect of Price ControlsWhen Demand Is InelasticQuantityPriceP0Q27P2Q3ABCQ2What would the deadweightloss be if QS=Q2?When price is regulated to be no lower than P2 only Q3will be demanded.Thedeadweight loss is givenby triangles

6、 B and CWelfare Loss When PriceIs Held Above Market-Clearing LevelQuantityPriceSDP0Q08竞争性市场的效率 n市场失灵：n外部性：市场价格无法反映的成本收益内容；n信息缺失：不完美信息导致消费者无法做出效用最大化决策。n在这种情况下政府干预市场将有可能增进效率；相反，在市场并未失灵的情况下政府干预将导致市场效率降低和无谓损失。9BAThe change in producersurplus will beA-C-D.Producersmay be worse off.CDPrice MinimumQuantity

7、PriceSDP0Q0PminQ3Q2If producers produce Q2,the amount Q2-Q3will go unsold.10BThe deadweight lossis given by triangles B and C.CAwminL1L2UnemploymentFirms are not allowed topay less than wmin.Thisresults in unemployment.SDw0L0The Minimum WageLw11价格支持和生产配额 n价格支持：n政府制定高于均衡价格的支持价格，再由政府购买过剩的供给；n这一政策常与减产或

8、限产的激励政策相结合。n政府成本：Ps(Q2-Q1)n无谓损失：消费者剩余+厂商剩余-政府成本=D-(Q2-Q1)ps 12BDATo maintain a price Psthe government buys quantity Qg.The change inconsumer surplus=-A-B,and the change in producer surplus is A+B+DD+QgQgPrice SupportsQuantityPriceSDP0Q0PsQ2Q113D+QgQgBAPrice SupportsQuantityPriceSDP0Q0PsQ2Q1The cost

9、to the government is the speckled rectanglePs(Q2-Q1)DTotalWelfareLossTotal welfare lossD-(Q2-Q1)ps14价格支持和生产配额n生产配额：n通过限制供给来提高商品价格。n对农民而言，价格支持和生产配额无差别，都使他们获得A+B+D的额外厂商剩余；n但对政府而言，两种政策就是有差别的，哪一种政策代价更大，应比较B+C+D（配额）和Ps(Q2-Q1)（价格支持）的大小。15BACDSupply RestrictionsQuantityPriceDP0Q0SPSSQ1Ps is maintained with

10、 and incentiveCost to government=B+C+D16Supply RestrictionsBAQuantityPriceDP0Q0PSSSDCn =A-C+B+C+D=A+B+D.nThe change in consumer and producer surplus is the same as with price supports.n =-A-B+A+B+D-B-C-D=-B-C.17进口限额和关税 n目的：n使进口商品国内价格高于国际价格，从而达到限制进口的目的。n进口配额或关税带来的福利损失：n国内厂商价格上涨，厂商剩余增加A；n消费者剩余损失由两部分构成

11、，因国内商品价格上升而导致的损失和因进口商品价格上升而导致的损失：A+B+C+D 18QSQDPWImportsABC By eliminating imports,the price is increased to PO.The gain is area A.Theloss to consumers A+B+C,so the deadweight loss is B+C.Import Tariff or QuotaThat Eliminates ImportsQuantityPriceHow high would a tariff haveto be to get the same resu

12、lt?DP0Q0SIn a free market,the domestic price equals the world price PW.19DCBQSQDQSQDAP*PwImport Tariff or Quota(general case)QuantityPriceDSnThe increase in price can be achieved by a quota or a tariff.nArea A is again the gain to domestic producers.nThe loss to consumers is A+B+C+D.20Import Tariff

13、or Quota(general case)nIf a tariff is used the government gains D,so the net domestic product loss is B+C.nIf a quota is used instead,rectangle D becomes part of the profits of foreign producers,and the net domestic loss is B+C+D.DCBQSQDQSQDAP*PwQuantityDSPrice21征税或补贴的影响 n征税：n买方价格卖方价格 n从量税征税后必须满足四个条

14、件：销售量和购买价格位于需求曲线上，QD=QD(Pb)销售量和销售价格位于供给曲线上，QS=QS(Ps)需求量=供给量，QD=QS 购买价与销售价之差为税收，Pb-PS=tax 22DSBDABuyers lose A+B,andsellers lose D+C,and the government earns A+D in revenue.The deadweightloss is B+C.CIncidence of a SpecificTaxQuantityPriceP0Q0Q1PSPbtPb is the price(includingthe tax)paid by buyers.PS

15、is the price sellers receive,net of the tax.The burdenof the tax is split evenly.23征税或补贴的影响n征税：n税收影响取决于供给和需求弹性；n一般来说，如Ed/Es较小，税负主要由买方承担，反之则由卖方承担。n转嫁因子：ES/(ES-Ed)转嫁因子趋近于1，税负主要由消费者承担；转嫁因子趋近于0，税负主要由厂商承担。24Impact of a Tax Dependson Elasticities of Supply and DemandQuantityQuantityPricePriceSDSDQ0P0P0Q0Q

16、1PbPStQ1PbPStBurden on BuyerBurden on Seller25征税或补贴的影响n补贴：n补贴可视为负税收，分析方法与上面相同。n在此种情况下，买方价格卖方价格，n如Ed/Es较小，补贴的好处主要归于消费者，反之则归于厂商。n补贴的四个条件类似于征税。26DSSubsidyQuantityPriceP0Q0Q1PSPbsLike a tax,the benefitof a subsidy is splitbetween buyers and sellers,dependingupon the elasticities ofsupply and demand.27二、

17、一般均衡 28一般均衡n局部均衡：n假设一种商品市场的行为不影响其他商品市场。n一般均衡：n将市场之间的反馈效应考虑在内去同时确定所有市场的价格和数量。n反馈效应：由相关市场的价格或数量变更而引起的一个市场的价格或数量的变更。n两个市场相互作用，最终走向一般均衡。29一般均衡n例子：n电影票和DVD租赁市场（互补品）。n图：PP31-32。n结论：未以一般均衡的观点考察市场之间的反馈效应，在这个例子里将导致低估税收效应；这在宏观经济政策的决策中十分重要。30DVDMTwo Interdependent Markets:Movie Tickets and Videocassette Rental

18、sPriceNumberof VideosPriceNumber ofMovie TicketsSMSV$6.00QMQV$3.00$6.35QMS*MAssume the governmentimposes a$1 tax on each movie ticket.QVDV$3.50General Equilibrium Analysis:Increase in movie ticket pricesincreases demand for videos.31DVDMTwo Interdependent Markets:Movie Tickets and Videocassette Rent

19、alsPriceNumberof VideosPriceNumber ofMovie TicketsSMSV$6.00QMQV$3.00The Feedback effects continue.$3.58Q*VD*V$6.35QMD*M$6.82Q*MS*MQVDV$3.50DMQ”M$6.75The increase in the priceof videos increases the demand for movies.32交换的效率 n帕累托效率：n无人可在不损害他人的前提下获益。n交换总是使双方获益的，换言之，交换总是促进帕累托改善的，直至达到帕累托效率状态，交换才停止。33两人模

20、型n假设：n两个消费者；两种商品；两人知道彼此的偏好（信息对称）；0交易费用。n埃奇沃斯盒子描述了交换发生的条件和效率的最终实现。n有效配置：n两消费者的边际替代率相等时实现，这在埃奇沃斯盒子里体现为两人的无差异曲线相切，此时实现了帕累托效率。n契约曲线：n埃奇沃斯盒子中所有两人无差异曲线相切的切点集合，它显示了所有的帕累托有效配置。34AA:UJ1=UK1,but the MRSis not equal.All combinationsin the shadedarea arepreferred to A.Gains fromtradeKarensClothingKarens FoodUK1

21、UK2UK3JamessClothingJamess FoodUJ1UJ2UJ3BCDEfficiency in Exchange10F0K0J6C10F6C35AKarensClothingKarens FoodUK1UK2UK3JamessClothingJamess FoodUJ1UJ2UJ3BCDEfficiency in Exchange10F0K0J6C10F6CIs B efficient?Hint:is theMRS equalat B?Is C efficient?and D?36The Contract Curve0JJamessClothingKarensClothing

22、0KKarens FoodJamess FoodEFGContractCurveE,F,&G arePareto efficient.If a change improvesefficiency,everyonebenefits.37竞争性市场的消费者均衡 n竞争性市场：n竞争性市场包含了众多的买者和卖者，因此任一方对交易条款不满，都可以很方便地另寻交易对方。n此时市场实现帕累托效率的条件是两种商品的相对价格比为1（对比两人模型的两人边际替代率相等）。38UK1UK2PPrice LinePPP is the price lineand shows possiblecombinations;s

23、lope is-1UJ1UJ2Competitive Equilibrium10F0K0J6C10F6CJamessClothingKarensClothingKarens FoodJamess FoodCABegin at A:Each James buys 2C and sells 2FEach James would move fromUj1 to Uj2,which is preferred(A to C).Begin at A:Each Karen buys 2F and sells 2C.Each Karen would move fromUK1 to UK2,which is p

24、referred(A to C).39UK1UK2PPrice LinePUJ1UJ2Competitive Equilibrium10F0K0J6C10F6CJamessClothingKarensClothingKarens FoodJamess FoodAt the prices chosen:Quantity fooddemanded(Karen)equals quantityfood supplied(James)-competitiveequilibrium.At the prices chosen:Quantity clothing demanded(James)equals q

25、uantityclothing supplied(Karen)-competitive equilibrium.CA40Competitive Equilibrium10F0K0J6C10F6CJamessClothingKarensClothingKarens FoodJamess FoodPPrice LineUJ1UK1APUJ2UK2C41竞争性市场的经济效率 n从C点可有如下几条结论：n两无差异曲线相切于C点，因此竞争性均衡配置C点是帕累托有效的；n此时两种商品的边际替代率等于它们的相对价格：n无差异曲线不相切则交易继续发生；n在无外部干扰的条件下竞争性均衡将自发实现；n福利经济学第

26、一定理：在一个竞争性市场中，一切互惠交易将实现，最终的资源的均衡配置在经济上将是有效率（帕累托有效）的。42公平与效率 n效用可能性边界：n显示了两消费者在契约曲线上实现了有效配置之后各自的效用水平。n效用可能性边界上的点是否还是公平的？对这一论断的判断取决于公平的定义。43H*Movement from one combination to another (E to F)reduces one persons utility.*All points on the frontier are efficient.Utility Possibilities FrontierJamess Util

27、ityOJOKEFGKarensUtilityL*Any point inside the frontier(H)is inefficient.*Combinations beyond the frontier(L)are not obtainable.Lets compareH to E and F.44社会福利函数n考虑到公平因素，在描述个体效用时还应引入社会福利函数。n平均主义：所有社会成员得到同等数量的商品；n罗尔斯主义：使境况最糟的人效用最大化；n功利主义：使社会所有成员的总效用最大化；n市场导向：市场结果就是最公平的。n如何界定公平，取决于使用了上述的哪一种公平定义。竞争性均衡导致

28、的帕累托有效结果可能是公平的，也可能不公平。45福利经济学第二定理 n公平的配置是否也要求帕累托有效呢？n福利经济学第二定理：n如果个人的偏好是凸的，则每种有效配置（契约曲线上的每一点）对于某些商品的初始配置而言都是竞争性均衡。n任何一种被认为是公平的均衡都可以通过资源在个人之间的适当配置来实现，而这样一种配置本身并不必然产生低效率。换言之，公平与效率并非绝对矛盾。n然而，社会中所有再分配收入的计划都是有成本的；因此，在实践上，公平和效率目标之间存在非此即彼的权衡关系。46生产的效率 n假设：n固定投入品：n劳动和资本；n两种产品：衣服和食物；n众多的投入要素供给者，他们通过出售其拥有的投入品

29、获得收入；n所获得的收入用于消费衣服和食物。n显然，n在这一框架下，供给和需求（消费者的收入和开支）是紧密联系的；n一种投入品价格的变化将引发收入和需求的变化，并产生反馈效应。4760F50F40L30LLabor in clothing productionEfficiency in Production50L0C0F30KCapitalin clothingproduction20L10L20K10K10L20L30L40L50LCapitalin foodproduction10K20K30K30C25C10C80FLabor in Food ProductionBCDAEach poi

30、nt measures inputs to the production A:35L and 5K-FoodB:15L and 25K-ClothingEach isoquant shows inputcombinations for a given outputFood:50,60,&80Clothing:10,25,&30EfficiencylA is inefficientlShaded area is preferred to AlB and C are efficientlThe production contract curve shows all combinations tha

31、t are efficient48竞争性投入品市场的生产均衡 n据上图：n竞争性市场产生有效生产点。n此时所有厂商的工资率（w）和资本价格（r）都相等，并都实现了生产成本最小化：nMRTS为等产量线的斜率；n竞争性均衡在生产契约曲线上；n竞争性均衡是有效率的。49生产可能性边界 n生产可能性边界：n显示以固定数量的劳动和资本能够生产的两种商品的所有组合，即生产契约曲线上的所有产量组合。n每点的斜率表示在该生产组合时的边际转换率MRT。n 50Production Possibilities FrontierFood(Units)Clothing(units)OF&OC are extremes

32、.Why is the productionpossibilities frontierdownward sloping?Why is it concave?B,C,&D areother possiblecombinations.AA is inefficient.ABCtriangle is also inefficientdue to labor marketdistortions.60100OFOCBCD51Production Possibilities FrontierFood(Units)Clothing(units)60100OFOCABCDB1C1FD2C1FMRT=MCF/

33、MCCThe marginal rate oftransformation(MRT)is the slope of thefrontier at each point.52产出效率n产出效率：n应以最小成本生产；n并且生产的商品组合应与人们购买它们的意愿相一致。n此时实现了有效产出及帕累托有效配置，MRS=MRT，因此有：53IndifferenceCurveOutput EfficiencyFood(Units)Clothing(units)60100ProductionPossibilitiesFrontierMRS=MRTCHow do you find theMRS=MRT combi

34、nationwith many consumerswho have differentindifference curves?54U2Competition and Output EfficiencyFood(Units)Clothing(units)60100AC1F1BC2F2A shortage of food and surplusof clothing causesthe price of foodto increase andthe price of clothing to decrease.CC*F*Adjustment continues untilPF=PF*and PC=P

35、C*;MRT=MRS;QD=QS for food and clothing.U155自由贸易的利益 n比较优势：n国家1生产一种商品的成本相对于生产其他商品来说比国家2生产该商品的成本低，国家1就在生产该商品方面对国家2具有比较优势。n绝对优势：n在所有商品生产上都占有绝对优势的国家将不会在所有商品生产上占有相对优势。n存在各自相对优势的国家就可以进行双边贸易，贸易将促使生产可能性边界外扩。56Hours of Labor Required to ProduceHolland12Italy63Cheese(1 lb.)Wine(1 gal.)Holland has an absolutead

36、vantage in both products.57Hours of Labor Required to ProduceHolland12Italy63Cheese(1 lb.)Wine(1 gal.)Hollands comparative advantageover Italy is in cheese:the cost of cheeseis 1/2 the cost of wine and Italys cost of cheese is twice the cost of wine.58Hours of Labor Required to ProduceHolland12Italy

37、63Cheese(1 lb.)Wine(1 gal.)Italys comparative advantage is wine,which is half the cost of cheese.59Hours of Labor Required to ProduceHolland12Italy63Cheese(1 lb.)Wine(1 gal.)Without Trade:Assume PW=PC in Holland&Italy.Holland has 24 hrs.of labor-max.wine=12 gals&max.cheese=24 lbs.or a combination60H

38、ours of Labor Required to ProduceHolland12Italy63Cheese(1 lb.)Wine(1 gal.)With Trade:Italy produces 8 gal.and trades 6;consumes 6 lbs.and 2 gals.Without Trade:3 lbs.and 2 gals.61Pre-trade pricesU1The Gains from TradeWine(gallons)Cheese(pounds)AWithout trade:production&consumption at A in Holland.MRT

39、=Pw/PC=2WorldpricesBCBWBWith trade(assume relativeprice Pw=PC):Produceat B,MRT=1CDWDDU2Consumption at D after trade.Holland imports the wind and exports cheese.Who gains and wholoses from trade?62竞争性市场的效率：总结 n经济效率的条件：n交换的效率：，在竞争性市场中就是n生产中投入品使用的效率：在竞争性市场中就是n产出市场的效率：在竞争性市场中：消费者在竞争性市场中实现效用最大化，必须满足 63市场

40、失灵的原因 n市场势力：n在商品市场中存在垄断，MR P；n比竞争性市场产出为少；n资源配置向其他市场；n于是导致无效率的配置。n不完全信息：n信息缺陷导致资源流动障碍。n外部性n当一种消费或生产活动对其他消费或生产活动产生不反映在市场价格中的间接效应时就存在外部性。n公共产品：n在计量消费时存在困难，于是市场对公共产品的提供将不足。64三、外部性与公共产品 65外部性 n负外部性：n一个群体的行为给其他群体造成成本。n正外部性：n一个群体的行为给其他群体带来收益。n边际外部成本与边际社会成本：n场景：钢铁厂将废水倾倒于河内，从而影响到下游渔民的生产成本。整个钢铁行业的废水倾倒与其产量相关联。

41、n边际外部成本：下游渔民在每一水平的钢铁产量上被强加的成本。n边际社会成本：MSC=MC+MEC 66MCS=MCIDP1Aggregate social cost ofnegativeexternalityP1q1Q1MSCMSCIWhen there are negativeexternalities,the marginalsocial cost MSC is higherthan the marginal cost.External CostsFirm outputPriceIndustry outputPriceMECMECIThe differences isthe margina

42、l externalcost MEC.q*P*Q*The industry competitiveoutput is Q1 while the efficientlevel is Q*.The profit maximizing firmproduces at q1 while the efficient output level is q*.67外部性导致无效率n负外部性使一些低效率的厂商继续保留在行业内，从而导致长期尺度上的过量生产。n正外部性则可能导致生产过少。68MCP1External BenefitsRepair LevelValueDIs research and develop

43、ment discouraged by positiveexternalities?q1MSBMEBWhen there are positiveexternalities(the benefitsof repairs to neighbors),marginal social benefitsMSB are higher thanmarginal benefits D.q*P*A self-interested home ownerinvests q1 in repairs.Theefficient level of repairsq*is higher.The higher priceP1

44、 discourages repair.69纠正市场失灵的方法 n假设：n市场失灵的原因是污染；n固定比例生产技术（要减少污染就必须减少生产，而产出的减少是通过征收产出税来实现的）；n通过改变技术，投入替代是可能的。70The Efficient Level of EmissionsLevel of Emissions246Dollarsper unitof Emissions02468101214161820222426MSCMCAE*The efficient level ofemissions is 12(E*)where MCA=MSC.Assume:1)Competitive mar

45、ket2)Output and emissions decisions are independent3)Profit maximizing output chosenAt Eo the marginalcost of abating emissionsis greater than themarginal social cost.E0At E1 the marginalsocial cost is greaterthan the marginal benefit.E1Why is this more efficientthan zero emissions?71排放标准与排放费n排放标准：n

46、对厂商可以排放的污染物设定法定上限，并通过经济惩罚或法律惩罚来维持；n排放标准的设定将导致生产成本加大，行业总价格提高。n排放费：n对厂商每单位废气进行收费。72排放标准与排放费n假设：n政策制定者有不对称信息；n管理成本客观上决定了对所有厂商适用同样的费率或标准。n排放费的优点：n当标准对所有厂商必须相同时，收费能以较低的成本实现同样的废气削减；n收费措施给厂商强烈的刺激去安装减少污染的新设备。n总结：n当MSC陡峭而MCA平缓时，设定排放标准占优；n在信息不完全时，设定标准使排放水平更确定，而减污成本更不确定；相反，收费使成本更确定而排放水平更不确定；n因此，哪种政策更好取决于不确定性的性

47、质和各成本曲线的形状。73Firm 2s ReducedAbatementCostsFirm 1s IncreasedAbatement CostsMCA1MCA2The Case for FeesLevel of Emissions246Fee perUnit ofEmissions01234567891011121313514The cost minimizing solutionwould be an abatement of 6for firm 1 and 8 for firm 2 andMCA1=MCA2=$3.3.752.50The impact of a standard ofa

48、batement of 7 for both firmsis illustrated.Not efficient becauseMCA2 MCA1.If a fee of$3 was imposedFirm 1 emissions would fallby 6 to 8.Firm 2 emissionswould fall by 8 to 6.MCA1=MCA2:efficient solution.74ABC is the increasein social cost less thedecrease in abatementcost.MarginalSocialCostMarginal C

49、ostof AbatementThe Case for StandardsLevel of EmissionsFee perUnit ofEmissions0246810121416246810121416EBased on incompleteinformation standard is 9(12.5%decrease).ADE m*.77Refundable DepositsAmount of Glass$DPrice falls to P and the amount of recycled glass increases to M*.SvSrSThe supply of glass

50、is the sum of the supplyof virgin glass(Sr)and the supply of recycledglass(Sr).M1PWithout refunds the price of glass is P and Sr is M1.SrSPM*With refunds Sr increasesto Sr and S increases to S.78外部性和产权 n产权是描述人们或厂商可以对他们的财产做什么的法律规则。n议价与经济效率 n当受外部性影响的群体较少并且产权良好界定时，经济效率将在没有政府干预的情况下实现。n科斯定理：当各方能够无成本地讨价还价