中财-微观经济学-第八章-利润最大化和竞争性供给

《中财-微观经济学-第八章-利润最大化和竞争性供给》由会员分享，可在线阅读，更多相关《中财-微观经济学-第八章-利润最大化和竞争性供给（84页珍藏版）》请在装配图网上搜索。

1、 第八第八章章 利润最大化和竞争性供给利润最大化和竞争性供给 本章概要本章概要完全竞争市场的利润最大化完全竞争市场的利润最大化以及短期、长期均衡以及短期、长期均衡1假设：厂商追求利润最大化假设：厂商追求利润最大化 不符合三条件不符合三条件定义：完全竞争市场定义：完全竞争市场分析框架：分析框架：结论结论 短期供给线；三种长期供给线短期供给线；三种长期供给线经验研究经验研究()()()()MR qMC qMR qMC qPMRAR符合三条件符合三条件竞争市场利润最大化与均衡竞争市场利润最大化与均衡短期均衡：短期供给短期均衡：短期供给线、生产者剩余线、生产者剩余长期均衡：长期供给长期均衡：长期供给线

2、线长期利润最大化受冲长期利润最大化受冲击：税收效应击：税收效应21.1厂商追求利润最大化的假设()()()max()qR qTC qq32.1完全竞争市场的定义完全竞争市场的定义 符合下面三个特征的市场称为完全竞争市场：符合下面三个特征的市场称为完全竞争市场：（1）产品同质）产品同质（Product homogeneity）；）；（2）厂商和消费者都是价格接受者）厂商和消费者都是价格接受者（Price taking）；）；（3）厂商无成本进入与退出）厂商无成本进入与退出（Free entry and exit）4IndustryD$4SPrice$per bushelOutput(millio

3、ns of bushels)100（1）产品同质：存在市场均衡价格P5d$4Output(bushels)Price$per bushel100200FirmIndustryD$4SPrice$per bushelOutput(millions of bushels)100DPP（2）价格接受者：厂商面临的需求线为6d$4Output(bushels)Price$per bushel100200FirmijPAVCiPAVCj（3）厂商无成本进退：，退出；，进入AVCiAVCj7P=MR=AROutput(bushels)Price$per bushel100200Firm2.2完全竞争市场的

4、重要性质完全竞争市场的重要性质PMRAR8证明()()()R qP qdR qMRPdqR qARPqPqMRARP对某厂商在完全竞争上某企业的 与 没有关系：93.1.分析框架：数学解分析框架：数学解221.1:()()()max()()()()()(max()0()()()0MR qMC qMRqR qTC qqdqdR qdTC qdqqMCdqdqqdqdqq由的一阶条件：的二阶条件：1.2:PMRAR由1.2()()()(:)MR qMC qMR qMC qPMRAR由1.1;10q210203040Price50MCAVCAC01234567891011Outputq*AR=MR=

5、PAq1:MR MCq2:MC MRq*:MC=MR q1Lost Profit for q2q*Lost Profit for q2q*3.2.分析框架：几何解分析框架：几何解11 当当MRMC时时 增加产量所增加的收益大于所增加的成本，因增加产量所增加的收益大于所增加的成本，因而总利润可以增加；而总利润可以增加；当当MRMC时时 减少产量所减少的收益小于所减少的成本，因减少产量所减少的收益小于所减少的成本，因而总利润可以增加；而总利润可以增加；当当MR=MC时时 无论怎样调整产量，总利润都只会减少而不会无论怎样调整产量，总利润都只会减少而不会增加。增加。1210203040Price500

6、1234567891011OutputMCAVCACq*AR=MR=PA4.1.短期均衡短期均衡MR=MC情形情形1：利润为正：利润为正()0qAR qAC q1310203040Price5001234567891011OutputMCAVCACq*AR=MR=PA情形情形2：利润为：利润为0()0qAR qAC q1410203040Price5001234567891011OutputMCAVCACq*AR=MR=PA情形情形3：弥补全部可变成本之外还能弥补部分固定成本：弥补全部可变成本之外还能弥补部分固定成本()0qAR qAC q1510203040Price500123456789

7、1011OutputMCAVCACq*AR=MR=PA情形情形4：刚好弥补全部可变成本，不能弥补一点固定成本：刚好弥补全部可变成本，不能弥补一点固定成本()0qAR qAC q1610203040Price5001234567891011OutputMCAVCACq*AR=MR=PA情形情形5：甚至不能弥补全部可变成本，更谈不上弥补一点固定成本：甚至不能弥补全部可变成本，更谈不上弥补一点固定成本()0qAR qAC q17关于短期均衡的总结关于短期均衡的总结 短期均衡的条件是：SMC=SMR=P 短期均衡中利润可能为正，为零，为负。18Price($perunit)OutputMCAVCACP

8、=AVCP2q2P1q1S4.2.1由短期均衡的五种情形可推导出由短期均衡的五种情形可推导出完全竞争厂商的短期供给线：几何完全竞争厂商的短期供给线：几何194.2.2由短期均衡的五种情形可推导出由短期均衡的五种情形可推导出完全竞争厂商的短期供给线：数学完全竞争厂商的短期供给线：数学11(1)min:()()(2)min:0(),min0,minPSAVCPSMC qqSMCPPSAVCqqSMCP PSAVCqPSAVC 20Price($perunit ofoutput)Output4.3.1由短期条件理解生产者剩余的定义：几何由短期条件理解生产者剩余的定义：几何CD214.3.2由短期条件

9、理解生产者剩余的定义：数学由短期条件理解生产者剩余的定义：数学000()()()()(0)()()00qqqPSPMC q dqPqMC q dqdTC qPqdqdqPqTC qTCPqVC qPqAVC qqABqDCqABCD22 生产者剩余与经济利润的区别生产者剩余与经济利润的区别PSRVCRVCFC23Price($perunit ofoutput)Output 市场的生产者剩余市场的生产者剩余24q1BCADPriceOutputP=MR=AR$40SACSMCq3LACLMC 4.4.1从从长期利润最大化长期利润最大化到长期均衡到长期均衡()LMRPLMC长期利润最大化条件：25

10、PriceOutputP=MR=AR$40q3LACLMC 4.4.2从从长期利润最大化长期利润最大化到到长期均衡长期均衡()();minLMRPLMCSMRPSMCSMCSAC PLAC长期均衡(零经济利润)条件：；P=MR=AR$4026 4.5行业的长期供给曲线行业的长期供给曲线11111111;tttttKLttttttttKKLLttttKKLLttttKKLLP KP LCKKLLPPPPPPPPPPPP比如：时：成本不变行业：成本递增行业：成本递减行业：27LACSMCq1D1S1Q1P1D2P2P2q2S2Q2OutputOutput$P1SL（1）成本不变行业）成本不变行业2

11、8OutputOutput$D1S1q1P1Q1P1SMC1LAC1SMC2LAC2P3S2P3Q3q2P2D2Q2P2（2）成本递增行业）成本递增行业29S2SLP3Q3P3SMC2LAC2OutputOutput$P1D1S1P1Q1q1SMC1LAC1q2P2D2Q2P2（3）成本递减行业）成本递减行业30Price($perunit ofoutput)OutputAVC1MC1P1q1MC2=MC1+taxAVC24.5长期利润最大化受到税收冲击的情形长期利润最大化受到税收冲击的情形q231 1212121290min:min:0PPAVCqqPAVCq教材的意思：32The Sver

12、iges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2009Elinor Ostrom 1/2USA Indiana University Bloomington,IN,USAb.1933 for her analysis of economic governance,especially the commons33The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2009Oliver E.Williamson1/

13、2USA University of California Berkeley,CA,USA b.1932 for his analysis of economic governance,especially the boundaries of the firm 3435Economic governance:the organization of cooperation Elinor Ostrom has demonstrated how common property can be successfully managed by user associations.Press Release

14、 12 October 200936Oliver Williamson has developed a theory where business firms serve as structures for conflict resolution.37Over the last three decades these seminal contributions have advanced economic governance research from the fringe to the forefront of scientific attention.38 Economic transa

15、ctions take place not only in markets,but also within firms,associations,households,and agencies.Whereas economic theory has comprehensively illuminated the virtues and limitations of markets,it has traditionally paid less attention to other institutional arrangements.39 The research of Elinor Ostro

16、m and Oliver Williamson demonstrates that economic analysis can shed light on most forms of social organization.40 Elinor Ostrom has challenged the conventional wisdom that common property is poorly managed and should be either regulated by central authorities or privatized.Based on numerous studies

17、 of user-managed fish stocks,pastures,woods,lakes,and groundwater basins,Ostrom concludes that the outcomes are,more often than not,better than predicted by standard theories.41 She observes that resource users frequently develop sophisticated mechanisms for decision-making and rule enforcement to h

18、andle conflicts of interest,and she characterizes the rules that promote successful outcomes.42Oliver Williamson has argued that markets and hierarchical organizations,such as firms,represent alternative governance structures which differ in their approaches to resolving conflicts of interest.43The

19、drawback of markets is that they often entail haggling and disagreement.The drawback of firms is that authority,which mitigates contention,can be abused.Competitive markets work relatively well because buyers and sellers can turn to other trading partners in case of dissent.44 But when market compet

20、ition is limited,firms are better suited for conflict resolution than markets.A key prediction of Williamsons theory,which has also been supported empirically,is therefore that the propensity of economic agents to conduct their transactions inside the boundaries of a firm increases along with the re

21、lationship-specific features of their assets.45Elinor Ostrom delivering a lecture at Indiana University,Bloomington,July 2008.46例题例题1320.12151055STCqqqP某完全竞争行业中单个厂商短期成本函数：（1）市场产品价格为时，厂商的短期均衡产量和利润；（2）当市场价格下降为多少时，厂商必须停产；（3）厂商的短期供给函数。4722*0.34150.34155520790PSMCdSTCSMCqqdqqqPqTRSTCPqSTC解：（1）483222220.1

22、2150.12150100.20min0.1 102 10 1555PAVCTVCqqqAVCqqqqdAVCqdqd AVCdqAVCP（2）49220.3415416 1.2(15)0.6(0.3415)PSMCqqPPqMRMCTRPqSTCdSTCMRPPMCdqPqq（3）0.640.64203416 1.2(15)0.641.22,50.60,5MRqMCqMRMCqPqPqPqP 50例题例题20.6103820,260SMCqTRqqSTC某完全竞争厂商的短期边际成本和总收益分别是：；并且时。求该厂商利润最大化时的产量和利润。51*()38,()38380.6103880PAR

23、MRTR qARqdTR qMRdqPpMCqq解：22()()()()()(0.610)0.31020,260340()38(0.310340)1580qTR qSTC qSTC qSMC qqdqqqTFCqSTCTFCqqqq52例题例题33220200600LTCqqqP某完全竞争市场上单个厂商的长期总成本：市场价格。（1）该厂商实现利润最大化的产量、平均成本和利润；（2）该厂商是否处于长期均衡？为什么？（3）该行业处于长期均衡时每个厂商的产量、平均成本和利润；（4）判断（1）中的厂商出于规模经济阶段还是规模不经济阶段？53223402002020200200800dLTCLMCqqd

24、qLMCPqLTCLACqqqPqLTC解：（1）22(2)01020min100600min10010;min100,06001200cdLACqdqd LACdqLACPLACqPLACLMCELAC，（3）（4）规模不经济54例题例题363004003000 1506,5080004004700 150DPSSPLACPqDPSSP某完全竞争市场需求函数为，短期市场供给函数为；单个企业在最低点的价格。（1）求市场的短期均衡价格和产量；（2）能否判断（1）中的市场处于长期均衡，求行业内的厂商数量；（3）如果市场需求变为，短期供给函数变为，求市场的短期均衡价格和均衡产量；（4）能否判断（3）

25、中的市场是否处于长期均衡，（5）如果（3）中的市场是处于长期均衡；判断该行业属于成本递增、不变还是递减行业。5563004003000 150639006min3900/5078DSSPPPqPLAC解：（1）（2）处于长期均衡。家180004004700 150656006minminttDSSPPPqPLACLAC （3）（4）不能,因为这个行业可能成本递增/不变/递减（5）成本不变行业56例题例题43240600LTCqqq在一个完全竞争的成本不变行业中单个厂商的长期成本函数求该行业的长期供给曲线。572224060038060020min2040 20600200200LTCLACqq

26、qdLTCLMCqqdqLACLMCqPLACP解:58例题例题5Suppose you are given the following information about a particular industry:Assume that all firms are identical,and that the market is characterized by pure competition.26500 100 Market demand1200 Market supply()722 Firm total cost function.200DSQPQPqLTC q59例题例题5(1)F

27、ind the equilibrium price,the equilibrium quantity,the output supplied by the firm,and the profit of the firm.60(1)5;60002200500(500)(500)528DSQQPQqPMCqPqC解:61(2)Would you expect to see entry into or exit from the industry in the long-run?Explain.What effect will entry or exit have on market equilib

28、rium?62(2)解：Entry because the firms in the industry are making positive profit.As firms enter,the supply curve for the industry will shift down and to the right and the equilibrium price will fall,all else the same.This will reduce each firms profit down to zero until there is no incentive for furth

29、er entry.63(3)What is the lowest price at which each firm would sell its output in the long run?Is profit positive,negative,or zero at this price?Explain.642(3)minmin2722200200722200722(200)380min(380)3.8PLACLMCLACqqqqqqqLAC q解:65(4)错题目错题目 What is the lowest price at which each firm would sell its o

30、utput in the short run?Is profit positive,negative,or zero at this price?Explain.662(4)20020022002000,03.8,0;3.8,0;qPMCqPAVCqqqPAVCPPP解:也就是只要就有所以只要就可销售.错解：67例题例题626300400()450 152115,DPC qqqP完全竞争市场需求函数为某竞争性厂商总成本函数如果市场价格为求企业生产的产量、利润以及生产者剩余。6815425(25)(25)800PMCqqPqC解：（1）2502502502()(115 154)(1004)100

31、 252 251250251250PSPMC q dqq dqq dq 也可以用图形解：（115-65）69例题例题72()500.50.08LTC qqqq每家商店冲洗胶卷的长期总成本为：为胶卷数。（1）如果冲洗一卷收费0.85美元，该行业是否处于长期均衡，如果不是，长期均衡的价格水平是多少？（2）如果行业调整到了长期均衡，现在出现一种新的冲洗技术，可以使冲洗成本下降25%，则单个商店最多愿意多少来购买这种新技术？708.50.50.1650(50)(25)150500.50.160.50.0825,4.5PMCqqPqLTCLMCLACqqqqP解：（1）22(2)().75(500.50

32、.08)37.50.3750.06()0.3750.12()4.534,33.39max33.39newnewnewCqqqqqMCqqMCqPqpayment71例题例题8 Consider a city that has a number of hot dogs stands operating throughout the downtown area.Suppose that each vendor has a marginal cost of$1.50 per hot dog sold,and no fixed cost.Suppose the maximum number of ho

33、t dogs any one vendor can sell in a day is 100.72(1)If the price of a hot dog is$2,how may hot dogs does each vendor want to sell?Since marginal cost is equal to 1.5 and the price is equal to 2,the hot dog vendor will want to sell as many hot dogs as possible,or in other words,100 hot dogs.73(2)If t

34、he industry is perfectly competitive will the price remain at$2 for a hot dog?If not,what will the price be?The price should fall to$1.50 so that price is equal to marginal cost.Each hot dog vendor will have an incentive to lower the price of a hot dog below$2 so they can sell more hot dogs than the

35、ir competitors.No hot dog vendor will sell a hot dog for a price below marginal cost,so the price will fall until it reaches$1.50.74(3)If each vendor sells exactly 100 hot dogs a day and the demand for hot dogs from vendors in the city is Q=4400-1200P,how many vendors are there?If price is 1.50 then

36、 Q=4400-1200*1.5=2600 in total.If each vendor sells 100 hot dogs then there are 26 vendors.75(4)Suppose the city decides to regulate hot dog vendors by issuing permits.If the city issues only 20 permits,and if each vendor continues to sell 100 hot dogs a day,what price will a hot dog sell for?If the

37、re are 20 vendors selling 100 hot dogs each then the total number sold is 2000.If Q=2000 then P=$2,from the demand curve.76(5)Suppose the city decided to sell the permits.What is the highest price a vendor would pay for a permit?At the new price of$2 per hot dog the vendor is making a profit of$0.50

38、 per hot dog,or a total of$50.This is the most they would pay on a per day basis.77例题例题9 A sales tax of$1 per unit of output is placed on one firm whose product sells for$5 in a competitive industry.78(1)How will this tax affect the cost curves for the firm?With the imposition of a$1 tax on a single

39、 firm,all its cost curves shift up by$1.Total cost becomes TC+tq,or TC+q since t=1.Average cost is now AC+1.Marginal cost is now MC+1.79(2)What will happen to the firms price,output,and profit?Since the firm is a price-taker in a competitive market,the imposition of the tax on only one firm does not

40、 change the market price.Since the firms short-run supply curve is its marginal cost curve above average variable cost and that marginal cost curve has shifted up(inward),the firm supplies less to the market at every price.Profits are lower at every quantity.80(3)Will there be entry or exit in the industry?If the tax is placed on a single firm,that firm will go out of business.81 8283演讲完毕，谢谢观看！