第22章FirmSupply中级微观经济学课件.ppt

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1、Chapter Twenty-TwoFirm Supply厂商供给厂商供给StructureuMarket environmentsuMarket demand for a competitive firmuShort-run supply decisionlUpward sloping MC curvelShut-down conditionuLong-run supply decisionuComparing long-run and short-run decisions.uProducers surplus and profitsFirm SupplyuHow does a firm

2、decide how much product to supply?This depends upon the firmsl technologyl market environmentl goalsl competitors behaviorsMarket EnvironmentsuAre there many other firms,or just a few?uDo other firms decisions affect our firms payoffs?uIs trading anonymous,in a market?Or are trades arranged with sep

3、arate buyers by middlemen?Market EnvironmentsuMonopoly(垄断）垄断）:Just one seller that determines the quantity supplied and the market-clearing price.uOligopoly（寡头垄断）寡头垄断）:A few firms,the decisions of each influencing the payoffs of the others.Market EnvironmentsuDominant Firm:Many firms,but one much la

4、rger than the rest.The large firms decisions affect the payoffs of each small firm.Decisions by any one small firm do not noticeably affect the payoffs of any other firm.Market EnvironmentsuMonopolistic Competition（垄断竞争）垄断竞争）:Many firms each making a slightly different product.Each firms output leve

5、l is small relative to the total.uPure Competition:Many firms,all making the same product.Each firms output level is small relative to the total.Market EnvironmentsuLater chapters examine monopoly,oligopoly,and the dominant firm.uThis chapter explores only pure competition.Pure CompetitionuA firm in

6、 a perfectly competitive market knows it has no influence over the market price for its product.The firm is a market price-taker.uThe firm is free to vary its own price.Pure CompetitionuIf the firm sets its own price above the market price then the quantity demanded from the firm is zero.uIf the fir

7、m sets its own price below the market price then the quantity demanded from the firm is the entire market quantity-demanded.Pure CompetitionuSo what is the demand curve faced by the individual firm?Pure CompetitionY$/output unitMarket SupplyMarket DemandpePure Competitiony$/output unitMarket Supplyp

8、epAt a price of p,zero is demanded from the firm.Market DemandPure Competitiony$/output unitMarket Supplypepp”At a price of p”the firm faces the entire market demand.At a price of p,zero is demanded from the firm.Market DemandPure CompetitionuSo the demand curve faced by the individual firm is.Pure

9、Competitiony$/output unitMarket Supplypepp”At a price of p”the firm faces the entire market demand.At a price of p,zero is demanded from the firm.Market DemandPure CompetitionY$/output unitpepp”Market DemandSmallnessuWhat does it mean to say that an individual firm is“small relative to the industry”

10、?uThe individual firms technology causes italways to supply only a small part of the total quantity demanded at the market price.The Firms Short-Run Supply DecisionuEach firm is a profit-maximizer and in a short-run.uQ:How does each firm choose its output level?The Firms Short-Run Supply DecisionuEa

11、ch firm is a profit-maximizer and in a short-run.uQ:How does each firm choose its output level?uA:By solvingThe Firms Short-Run Supply DecisionCase(a)ys*0:P P(y)yys*The Firms Short-Run Supply DecisionFor the interior case of ys*0,the first-order maximum profit condition isThat is,So at a profit maxi

12、mum with ys*0,themarket price p equals the marginalcost of production at y=ys*.uMRMCuMR 0,the second-order maximum profit condition isThat is,So at a profit maximum with ys*0,thefirms MC curve must be upward-sloping.The Firms Short-Run Supply Decision$/output unitypeys*yMCs(y)The Firms Short-Run Sup

13、ply Decision$/output unitypeys*yAt y=ys*,p=MC and MCslopes upwards.y=ys*is profit-maximizing.MCs(y)The Firms Short-Run Supply Decision$/output unitypeys*yAt y=ys*,p=MC and MCslopes upwards.y=ys*is profit-maximizing.At y=y,p=MC and MC slopes downwards.y=y is profit-minimizing.MCs(y)The Firms Short-Ru

14、n Supply Decision$/output unitypeyAt y=ys*,p=MC and MCslopes upwards.y=ys*is profit-maximizing.So a profit-max.supply level can lie only on the upwards sloping part of the firms MC curve.MCs(y)ys*The Firms Short-Run Shut-Down ConditionuBut not every point on the upward-sloping part of the firms MC c

15、urve represents a profit-maximum.uBut not every point on the upward-sloping part of the firms MC curve represents a profit-maximum.uThe firms profit function isuIf the firm chooses y=0 then its profit isThe Firms Short-Run Shut-Down Condition uSo the firm will choose an output level y 0 only ifThe F

16、irms Short-Run Shut-Down ConditionuSo the firm will choose an output level y 0 only ifuI.e.,only ifEquivalently,only ifThe Firms Short-Run Shut-Down ConditionAVCs(y)ACs(y)MCs(y)$/output unityThe Firms Short-Run Shut-Down ConditionAVCs(y)ACs(y)MCs(y)$/output unityThe Firms Short-Run Shut-Down Conditi

17、onAVCs(y)ACs(y)MCs(y)$/output unityp AVCs(y)The Firms Short-Run Shut-Down ConditionAVCs(y)ACs(y)MCs(y)p AVCs(y)ys*0.$/output unityThe Firms Short-Run Shut-Down ConditionThe Firms Short-Run Supply DecisionAVCs(y)ACs(y)MCs(y)p AVCs(y)ys*0.The Firms Short-Run Supply DecisionAVCs(y)ACs(y)MCs(y)p AVCs(y)

18、ys*0.The Firms Short-Run Supply DecisionAVCs(y)ACs(y)MCs(y)The firms short-runsupply curveShutdown point$/output unityThe Firms Short-Run Supply DecisionuShut-down is not the same as exit.uShutting-down means producing no output(but the firm is still in the industry and suffers its fixed cost).uExit

19、ing means leaving the industry,which the firm can do only in the long-run.The Firms Long-Run Supply DecisionuThe long-run is the circumstance in which the firm can choose amongst all of its short-run circumstances.uHow does the firms long-run supply decision compare to its short-run supply decisions

20、?The Firms Long-Run Supply DecisionuA competitive firms long-run profit function isuThe long-run cost c(y)of producing y units of output consists only of variable costs since all inputs are variable in the long-run.The Firms Long-Run Supply DecisionuThe firms long-run supply level decision is touThe

21、 1st and 2nd-order maximization conditions are,for y*0,The Firms Long-Run Supply DecisionuAdditionally,the firms economic profit level must not be negative since then the firm would exit the industry.So,The Firms Long-Run Supply DecisionMC(y)AC(y)y$/output unitThe Firms Long-Run Supply DecisionMC(y)

22、AC(y)y$/output unitp AC(y)The Firms Long-Run Supply DecisionMC(y)AC(y)y$/output unitp AC(y)The Firms Long-Run Supply DecisionMC(y)AC(y)y$/output unitThe firms long-runsupply curveY$/output unitLMC=long-run supplyCminLong-Run Constant Average CostsThe Firms Long-Run Supply DecisionuHow is the firms l

23、ong-run supply curve related to all of its short-run supply curves?The Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitACs(y)MCs(y)The Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitACs(y)MCs(y)pys*y*ys*is profit-maximizing in this short-run.The Firms Long&Short-Run Supply

24、 DecisionsMC(y)AC(y)y$/output unitACs(y)MCs(y)pys*y*ys*is profit-maximizing in this short-run.P PsThe Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitACs(y)MCs(y)pys*y*The firm can increase profit by increasingx2 and producing y*output units.P PsP PThe Firms Long&Short-Run Supply Decisi

25、onsMC(y)AC(y)y$/output unitACs(y)MCs(y)p”ys*ys*is loss-minimizing in this short-run.The Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitACs(y)MCs(y)p”ys*ys*is loss-minimizing in this short-run.LossThe Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitACs(y)MCs(y)p”ys*This los

26、s can be eliminated in the long-run by the firm exiting the industry.LossThe Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitThe Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitpys*ys*is profit-maximizing in this short-run.The Firms Long&Short-Run Supply DecisionsMC(y)AC(y)

27、y$/output unitpys*ys*is profit-maximizing in this short-run.P PsThe Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitpys*ys*is profit-maximizing in this short-run.y*is profit-maximizing in the long-run.y*The Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitpys*ys*is profit-ma

28、ximizing in this short-run.y*is profit-maximizing in the long-run.y*P PThe Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitpys*y*P PsP PThe firm can increase profit by reducingx2 and producing y*units of output.The Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitThe Firms L

29、ong&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitThe Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitThe Firms Long&Short-Run Supply DecisionsMC(y)AC(y)y$/output unitShort-run supply curvesLong-run supply curveLong Run and Short Run SupplyuThe long-run supply curve is more elastic

30、than the short-run supply curve.uBecause the firm has more leeway in adjusting supply in the long-run than in the short run.附加之言：自由市场还是凯恩斯主义？被遗忘的奥地利学派u斯密：斯密：“自然的自由体系自然的自由体系”u1933.钱伯林钱伯林垄断竞争理论垄断竞争理论 罗宾逊罗宾逊不完全竞争经济学不完全竞争经济学 观点：存在垄断观点：存在垄断 政策含义：政府干预、反垄断、反托拉斯政策含义：政府干预、反垄断、反托拉斯u反托拉斯法：反托拉斯法：1890the Sherman

31、 Antirust Act of 1890 1936the Robinso-Patman Act of 1936u案例案例:IBM1969（不了了之）；（不了了之）；Microsoft 1997案（案（600多万美元罚金）多万美元罚金）u奥地利学派：反托拉斯法没有必要，反生奥地利学派：反托拉斯法没有必要，反生产力和违背自由产力和违背自由u确定一个产业的最佳厂商数量是不可能的确定一个产业的最佳厂商数量是不可能的（Mises,1966）。最好的模型是能够经得）。最好的模型是能够经得起起“市场检验市场检验”的模型。的模型。“市场检验市场检验”是是一个试错的过程，在这个过程中每个行业一个试错的过程，在

32、这个过程中每个行业确定自己的最佳规模，并通过竞争性利润确定自己的最佳规模，并通过竞争性利润追求确定其价格结构（追求确定其价格结构（Hayek，1978）u垄断公司在成长阶段是高度创新的公司，并需要垄断公司在成长阶段是高度创新的公司，并需要要大量的风险资本投资，垄断公司也能带来激烈要大量的风险资本投资，垄断公司也能带来激烈的竞争，从而会有后来者居上，新崛起的垄断公的竞争，从而会有后来者居上，新崛起的垄断公司取代老的垄断公司（司取代老的垄断公司（Schumpter，1950）。）。u直到直到1850年，垄断一词一直是指美国国会授予的年，垄断一词一直是指美国国会授予的排他的贸易权力。排他的贸易权力。

33、u可用垄断的定义只有一个，就是政府给予的特权，可用垄断的定义只有一个，就是政府给予的特权，解决措施也只有一个，就是政府降低垄断，就是解决措施也只有一个，就是政府降低垄断，就是政府消除自己的垄断（政府消除自己的垄断（Rothbard，1962）u政府，而不是市场，是垄断之源。政府的授权、政府，而不是市场，是垄断之源。政府的授权、认证、特许、关税和其他法定措施才能创造垄断；认证、特许、关税和其他法定措施才能创造垄断；拥有垄断能力的特殊经济组织便不再参与公开竞拥有垄断能力的特殊经济组织便不再参与公开竞争（争（Armentanono，1990）u不去控制经济中的垄断而承受其负面效不去控制经济中的垄断而

34、承受其负面效应比去控制它而承受不理想的政治要更应比去控制它而承受不理想的政治要更好好贝克尔。贝克尔。u芝加哥学派的芝加哥学派的“微观先生微观先生”斯蒂格斯蒂格勒：类似完全竞争模型（勒：类似完全竞争模型（theory of pirce,1987）不受压制的市场类似于完全竞争。大厂不受压制的市场类似于完全竞争。大厂商行为类似完全竞争商行为类似完全竞争u实验经济学证据：当一个行业只有几个实验经济学证据：当一个行业只有几个大公司时，行业内的竞争未必降低。大公司时，行业内的竞争未必降低。弗农弗农.史密斯史密斯Producers Surplus RevisiteduThe firms producers

35、surplus is the accumulation,by extra unit of output,of extra revenue less extra production cost.uHow is producers surplus related to profit?Producers Surplus Revisitedy$/output unitAVCs(y)ACs(y)MCs(y)pPSy*(p)Producers Surplus RevisitedSo the firms producers surplus isThat is,PS=Revenue-Variable Cost

36、.Producers Surplus Revisitedy$/output unitAVCs(y)ACs(y)MCs(y)py*(p)Producers Surplus Revisitedy$/output unitAVCs(y)ACs(y)MCs(y)py*(p)Revenue=py*(p)Producers Surplus Revisitedy$/output unitAVCs(y)ACs(y)MCs(y)py*(p)Revenue=py*(p)cv(y*(p)Producers Surplus-1y$/output unitAVCs(y)ACs(y)MCs(y)pPSy*(p)Producers Surplus-2y$/output unitAVCs(y)ACs(y)MCs(y)py*(p)Producers Surplus RevisiteduPS=Revenue-Variable Cost.uProfit=Revenue-Total Cost =Revenue-Fixed Cost -Variable Cost.uSo,PS=Profit+Fixed Cost.uOnly if fixed cost is zero(the long-run)are PS and profit the same.