第九章垄断竞争和寡头2.ppt

1、寡头垄断,主要内容: 寡头垄断市场的特点 斯威齐模型 寡头厂商之间的博弈 对寡头垄断市场的评价,Oligopoly Defined,数量有限的少数企业占据产业的主导地位。 寡头垄断企业的经营战略（行为）相互影响。每一企业在做出行动决策时，都要考虑其他企业将做出的反应。,一、 寡头垄断市场的条件,At The Same Time,Given the small number of firms, oligopolists have a much better chance of colluding than monopolistic competitors.容易形成共谋 It is this st

2、rategic decision making and possibility of collusive behavior that makes oligopoly so interesting.,A Few Questions,In analyzing oligopoly, what we ultimately want to answer are these questions: 什么因素导致寡头垄断的产生？ 寡头垄断市场的功能特征。 这种市场功能有怎样的市场绩效？,Sources Of Oligopoly,进入的障碍导致寡头垄断的产生。,#1: Scale-Economy Barrier

3、s to Entry,Recall that with monopoly, average costs decrease throughout the relevant range of production so that one firm is able to eventually drive out all other firms by producing at lowest cost. With oligopoly, it is a few firms - not just one that drive every one else out.,Minimum efficient sca

4、le for a firm in this industry is a plant size of AC, which equals one third of the total output AD.,Aggregate costs per unit of output.,Output,A B C D,constant returns to scale,decreasing returns to scale,Average Total Cost Curve for an Oligopolistic industry,Minimum Efficient Scale,The smallest le

5、vel of output at which a firm can minimize long-run average costs. In the case of natural monopolies like the railroads and utilities, small firms cannot realize the MES the minimum efficient scale - so there is only one seller. A large minimum efficient scale can also give rise to oligopoly.,The En

6、try Dilemma,Assume three big firms in this industry all producing an output of AC at their MES with an equal share of the market. Can you see the dilemma for a new firm trying to enter this industry?,Easily Forced Out,If the new firm tries to enter the industry at a plant size less than the MES say

7、at output AB - it will be a higher cost producer than its rivals and will be highly vulnerable to being driven out of the industry by its competitors. All its rivals need to do is set price below the new firms costs for a while, cause it to incur heavy losses, and eventually, it will withdraw.,Alter

8、natively,If the firm builds a plant size at the MES to be competitive, it will have to seize a sizeable market share from its rivals to achieve efficient production. It would have to cut each of its rivals back from a third to a fourth of the national market; and the likely result would be losses fo

9、r everyone. It is perhaps not surprising that scale-economy barriers deter entry into the industry and preserve the oligopolistic structure.,It simply requires a lot of capital investment to set up the elaborate plant and equipment necessary to produce. The broader problem is that established firms

10、with a track record may have better access to lower cost capital than new entrants.,#2: Large Capital Requirements,For Example,A large, existing firm with an established reputation will likely be able to borrow money at a significantly lower interest rate than a new firm without a track record.,Aggr

11、egate costs per unit of output.,Output,New Firm,Old firm,#3: Absolute Cost Advantange,One source of such barriers is that established firms may possess valuable know-how in production or so-called trade secrets. One of the best kept secrets in the industrial world is the secret ingredient in Coca Co

12、la. Only a few executives in the company know what it is.,Trade Secrets,Patents,An existing firm may have patents granting it exclusive rights to certain product features or production processes.,Raw Materials,#4:Product DifferentiationBarriers to Entry,Any new firm entering the market would have to

13、 incur substantial advertising costs just to enjoy the same size and inelasticity of demand for its product.,The Bottom Line,Barriers to entry play a very important role in creating and sustaining oligopolistic industries. Why should we worry about this particular market structure? The answer lies i

14、n better understanding the concepts of market power and market concentration.,Market Power,Market power signifies the degree of control that a firm or a small number of firms has over the price and production decisions in an industry. The most common measure of market power is the four-firm concentr

15、ation ratio.,Strategic Interaction,Concentration ratios are important because they help serve as an indicator of the degree of strategic interaction that might occur in an industry. Strategic interaction is a term that describes how each firms business strategy depends on their rivals strategies.,Mu

16、tual Interdependence Recognized,由于产业内部企业数量减少，产业集中度提高，每一企业在进行产量和价格决定时，都要考虑竞争对手由此做出的反应。 一旦这种相互依赖 、相互影响的行为机制被认识到，厂商只能在合作和非合作行为中选择其一。,Noncooperative Behavior,当一个厂商与其他厂商没有任何显性和隐性的合约时，厂商的行为是独立的。 This typically characterizes monopolistic competition.,Cooperative Behavior,为了尽可能 减少竞争，厂商间达成有关价格、产量或其他市场运作方面的显性

17、和隐性合约，形成厂商间行为的合作。,Collusion,When firms in an oligopoly act cooperatively, they must engage in some form of collusion. 当企业联合决定他们的价格、产量或者共同决定各自占有的市场份额时，共谋就产生了。 这种共谋可以是显性的也可以是隐性的。,One example of explicit collusion would be that of the Gilded Age（美国镀金时代，南北战争后35年间） oligopolists in the early years of Amer

18、ican capitalism.,这些寡头垄断者建立托拉斯或者卡特尔以控制价格。,Explicit Collusion,The Antitrust Laws,当美国人认识到需要对垄断进行控制并于1910年通过了反托拉斯法以后，卡特尔等显性的共谋行为就变成了非法行为。,Tacit Collusion,因为反托拉斯法的限制，显性的共谋行为是非法的，隐性共谋成为一种选择。 The word tacit means to “express or carry on without words or speech.” 隐性共谋意味着在没有显性合约的前提下实现了企业间对竞争的限制。,How They Do

19、It,实现隐性共谋的的一个共知的方式是行业领先的企业管理者通过公众场合下的演说表达共谋的可能性。 在这些演说中，当演说者提出行业成本提高因此价格也必须提高时，他是有所指的，有特别的用意。 特是通过媒体向其他企业的管理者传达一种特别的信息，而这时合法的。,The Role of Trade Associations,行业协会在企业间实现隐性共谋方面起到了重要的作用。 这样的行业协会是有关企业价格和成本方面的信息的交流和传递中心。 通过这些信息，管理者可以更好的掌握竞争对手的动态，并为联合行动准备基础。,The Upshot,当企业间实现了隐性共谋，但们就会制定一个明显的高价格以实现更大的利润或者

20、减少经营的风险。,Models Of Oligopoly Conduct,现在我们讨论一些有关刻画寡头垄断行为的不同模型。 这些模型涉及到经济学的分支学科产业经济学和博弈理论的相关内容。 In doing so, please keep in mind two major points.,The Major Points,首先没有一个单一的模型用于解释寡头垄断的所有行为，而是存在许多模型，每一个模型都在解释寡头垄断行为方面有独特的应用价值。 第二，我们只是涉及到产业组织理论和博弈论的一点皮毛，因此分析问题的过程中，只是把问题描述清楚，而没有涉及这些理论本身的相关内容。,研究寡头垄断厂商行为的模

21、型有两类： 一类是非勾结性的寡头垄断模型，这种模型是假设对手的反应方式一经确定后就保持不变并重复出现。典型的非勾结性寡头垄断模型有：古诺模型、斯威齐模型。 一类是勾结性寡头垄断模型，即寡头垄断厂商为避免由于相互依存所产生的不确定性和竞争而导致的两败俱伤，从而进行的某种形式的勾结或串谋。典型的勾结性寡头垄断模型有：卡特尔模型,Three Basic Models,The Cartel Model,当共谋实现了的情况下，寡头垄断厂商如何决定他们的价格和产量,The Kinked Demand Theory,提供一个为什么寡头垄断厂商会取得一个垄断高价的解释。,Game Theory,Once we

22、 come to understand these models, we can move on to the richer and more complex and modern realm of game theory.,二、古诺模型（双寡头模型） 早期的寡头模型，法国经济学家古诺于1838年提出。 由两个寡头的垄断厂商，也被称为双寡头模型，但是结论可以容易的推广到三个或者三个以上的寡头厂商的情况中。 假定：市场上有A和B两个厂商，生产销售相同的产品，生产成本为零；他们共同面临的需求线是线性的，两个厂商都准确的知道市场需求线是什么；两个厂商都是在已知对方的产量的前提下，各自决定能够给自己带

23、来最大利润的产量。,Q,P,Qe,Pe,D=f(P),P1,P2,Q1,Q2,G,F,H,古诺模型,A厂商首先进入市场，由于生产成本为零，因此厂商的收益等于它的利润。A厂商将自己的产量定义为市场总容量的1/2，即OQ1=1/2OQe，将价格定位在OP1，从而实现利润最大化，利润为图中矩形 OP1 FQ1面积。 B厂商进入市场时知道A厂商给自己留下的份额只有1/2OQe ，B厂商按照相同的行为方式确定自己的产量和价格，即生产剩余市场容量的1/2，Q1Q2=1/4OQe，市场价格降为OP，B场上获得的利润相当于矩形Q1HGQ2的面积。此时A厂商因为B厂商的进入导致价格下降从而利润减少为矩形OP2

24、HQ1的面积。,A厂商知道B厂商留给自己的市场空间为3/4OQe，为了实现利润最大化，将自己的产量定位为3/8OQe。与上一次相比，产量减少了1/8OQe，然后B场上再次进入市场，A厂商留给B厂商的市场容量只有5/8OQe，于是B场上定义自己的产量为5/16OQe，与上一次相比，B厂商产量增加了1/16OQe。 这一过程不断重复下去的结果是每一厂商都只生产1/3的市场容量的产量，行业总供给量为市场容量的2/3。,A厂商的均衡产量为,B厂商的均衡产量为,古诺模型的推广 令寡头厂商的数量为m，结论为 每个寡头厂商的产量为市场总容量的1/m+1。 行业的总产量为市场总容量的m/m+1。,古尔诺模型,

25、基本假定是:由A、B两个企业组成的寡头垄断模型，他们彼此独立行动，产品完全替代，各自追求各自的利润最大化。,两寡头垄断企业共同面对的需求曲线为： P f (QA+QB) 则A、B两企业的利润函数分别为： APQATCA f（QAQB）QATCA bPQB TCBf（QAQB）QBTCB,若这两个企业的边际成本函数已知，则通过以上两式就不难解出这两个企业的产销量，并进而得到市场价格，这就是古尔诺均衡点。,A，B 两企业各自追求各自的利润最大化，利润最大化的必要条件是：,P=1500-Q=1500-（QA+QB） A=TRA-TCA =p* QA 0 =1500- （QA+QB）* QA =150

26、0 QA QA2 QA QB 求利润最大化的一阶条件并令其等于0 1500-2 QA -QB=0 QA =750- QB /2,P=1500-Q=1500-（QA+QB） B=TRB-TCB =p* QB 0 =1500- （QA+QB）* QB =1500 QB QB2 QA QB 求利润最大化的一阶条件并令其等于0 1500-2 QB -QA=0 QB=750- QA /2 QA =750- QB /2 QA = QB =500 QA = QB =1500/3=500,三、The Kinked Demand Curve弯折的需求线（斯威齐模型）,1939年提出的价格刚性的模型，即当需求或成

27、本发生变化时，价格却不变。有时又将之称为价格不对称竞争模型。这一模型用于解释为什么在寡头垄断市场上价格具有僵固性特征。 同时也有助于解释为什么在寡头垄断市场上即使不存在共谋行为，价格也会高于完全竞争市场。,基本设定前提：弯折需求曲线模型是一类重要的寡头垄断市场模型，又称为斯威齐（Sweezy）模型。模型的基本设定前提是：在既定的市场价格水平上，任何一个寡头垄断者都不敢随意变动其销售量和价格，如果其中一个厂商提高价格，其它厂商因为担心销售量减少而不会跟着提价；如果其中一个厂商降低价格，则其它厂商必定也会跟着降价竞相销售，以争取更多的销售量。 假定： 寡头垄断厂商推测其他厂商对自己价格的态度是：跟

28、跌不跟涨,An Example,假设在一个寡头垄断市场上存在三个企业 A, B, C, 每一个企业占有整体市场的三分之一份额。 进一步假设每一个企业独立作出价格决策，相互之间没有价格共谋。,Price,Quantity,d,Q,MR,P,A Kinked Demand Curve,D,What does the firms demand curve look like?,If Firm A raises its price, and the firm believes that the other firms wont go along, its perceived demand curve

29、for increasing price will be very elastic.,Price,Quantity,d,Q,MR,P,D,B,d,D,Price,Quantity,Q,P,Alternatively, suppose Firm A decides to lower its price. What might it most logically expect its rivals to do? a) Ignore the price decrease and lose market share to Firm A. b) Match the price decrease and

30、maintain their market shares relative to Firm A. c) Invite the CEO of Firm A to Vegas for a little secret chat.,D1,MR,D2,Price,Quantity,Q,MR,P,Alternatively, suppose Firm A decides to lower its price. What might it most logically expect its rivals to do? a) Ignore the price decrease and lose market

31、share to Firm A. b) Match the price decrease and maintain their market shares relative to Firm A. c) Invite the CEO of Firm A to Vegas for a little secret chat.,D2,D1,Price,Quantity,Q,MR,P,Firms perceived demand curve,c,d,P,Q,P3,Q3,假设寡头垄断厂商以价格P1出售商品，在此价格上的销售为Q1。如果寡头垄断厂商把价格降至P2，其它寡头垄断厂商必定也会跟着降价竟相销售，这

32、使得该寡头的企图受到影响，销售量只能是Q2；如果寡头垄断厂商把价格升至P3，由于其它厂商不降价，该寡头处于高价销售状态，从而会失去更多的顾客。销售量只能是Q3。由此可见，在模型的设定之下，寡头所面对的需求曲线是一条弯折的曲线，一段弹性大，另一段弹性小。,d,D,P1,P2,Q1,Q2,A,厂商的行为分析,P,O,Q,P0,MC1,MR,D,q0,mr,A,B,C,MC2,MC3,斯威齐模型,这一模型指出：寡头垄断的个别厂商，面对的需求曲线在某一价格水平上会出现折弯的现象，因此，这一模型又被称为折弯的需求曲线模型。它可以很好地解释寡头市场上的价格刚性问题。,三、卡特尔模型,卡特尔（cartel）

33、是寡头之间以公开或正式的方式进行互相勾结的一种形式。 它是同一个行业的独立的厂商之间通过有关价格、产量和市场的划分等事项达成明确的协议而建立的垄断组织。 任务：为各个成员的厂商的同质产品制定统一的定价，然后在各个厂商之间分配产量。 作用：避免损失，增加总利润，阻止其他厂商进入，减少威胁。,寡头垄断者的共谋以及联合利润最大化,卡特尔模型提供了一个在共谋实现后的厂商价格和产量决定的解释。,Consider A Four-Firm Industry,假设每一厂商都已经非常厌恶价格竞争。 他们在每年一度的峰会上，无视反垄断法的约束而秘密举行共谋的会议。,A Negotiated Price,他们确定一

34、个秘密的行业价格，为保证行业价格的实施，同时确定相互之间的产量规模比例。,A Question,So where do you think these oligopolies will set price? a) The oligopoly will set price equal to marginal cost. b) The oligopoly will set marginal revenue equal to marginal cost. c) This is an incredibly（不可思议的）obscure（模糊的） question.,The Answer,So where

35、 do you think these oligopolists will set price? a) The oligopoly will set price equal to marginal cost. b) The oligopoly will set marginal revenue equal to marginal cost. c) This is an incredibly obscure question.,If the oligopolists can truly coordinate their activities, the obvious price to set i

36、s the same as that which would be set by a monopolist.,Joint Profit Maximization Model,Price will be set by the profit-maximizing rule of marginal revenue equals marginal cost. If price is set at that point, the oligopolists will jointly maximize their profits, which is why this model is often calle

37、d the joint profit maximization model.,One Other Point,In order for the monopoly price to hold in the marketplace, total industry output must equal the monopoly output. This is where problems with the cartel are likely to emerge because if any one firm in the oligopoly decides to cheat by producing

38、more than its agreed upon share of output, it can make higher profits than if it adheres依附遵从 to the cartel agreement.,The OPEC Cheating Example,In the days of 1973 and 1974, few, if any economists, believed OPEC would turn out to be such a paper tiger. 在这期间， OPEC成员国为反对美国对以色列的支持，使输往美国的石油价格上升了四倍。,The

39、Result,这对美国经济造成了严重影响。 Under international law, OPECs cartel behavior was quite legal even if cartels are illegal within the U.S.,After The 1970s,The OPEC cartel has been unable to keep the price of oil high, and at least part of the problem has been on the demand side. 1970年代以后，由于石油危机的冲击，消费者开始使用节约燃料

40、的汽车，生产者也在几乎所有的领域开始了节约能源的计划。,At The Same Time,在供给方面，高价格刺激了对石油资源的探寻，许多非OPEC国家比如挪威和墨西哥加入了石油供给国的行列。,Nonetheless,主要的问题还不在这方面， OPEC 内部面临相互之间的欺骗行为问题。 这是因为各成员国之间在经济和政治上存在巨大的差异，因而相互之间存在不信任。,The Wealthier Countries,一些高收入的富裕国家比如 Saudi Arabia, Kuwait, Qatar 等非常愿意控制产量以实现高额利润。,The Poorer Countries,其他一些贫穷的国家比如 委内瑞

41、拉、尼日利亚不可能控制对其他国家的欺骗，因为他们面临严重的外债。,Cheating Occurs,Cheating has arisen with other nations like Iran, Iraq, and Libya. They have used their oil wealth to fund military operations against their neighbors.,The End Result,After adjusting for inflation, the price of oil in the 1990s is actually less than i

42、t was at the beginning of the 1970s before OPEC raised the price.,The Broader Problem,OPEC has no effective enforcement mechanism to police its agreements. It has little effective way to punish any members who do cheat on the collusive bargain.,四、对寡头垄断市场的评价,寡头垄断市场模型很多，依竞争对手的不同反应来决定自己的价格与产量； 一般情况下，价格

43、水平较高，产量较少，所获利润较多，因此在社会经济效率方面有不良效果，如资源浪费，消费者负担加重等； 有利的地方：有利于产品的创新与改进，有利于需要大量投资、专业化水平高的产品的生产，产品差别可以满足消费者的不同偏好。在完全竞争市场和完全垄断市场中，很少有对研究与开发的刺激。而且，完全竞争厂商与垄断竞争厂商一样，通常力量较小，无力承担研究工作。,Game Theory,五、 博弈论入门,当在决策过程中必须考虑其行为对竞争对手的影响以及竞争对手的反应时，就进入了博弈论分析的领域。,（一）博弈论简介 基本概念,博弈论（Game Theory）直译为“游戏理论”。在英语中，game 指人们在确定规则下

44、的一种游戏、活动，在这个活动中，每个主体都努力达到自己的目标。 汉语里“游戏”一词有儿戏的味道，且“游戏理论”不太严肃，所以把它译为“博弈论”。,约翰纳什（JohnNash）,The Prisoners Dilemma,Lets look at the Prisoners Dilemma, a well-known game that demonstrates the difficulty of cooperative behavior in certain circumstances.,Two suspects in a bank robbery Bonnie and Clyde are a

45、rrested and interrogated拘留审讯 in separate rooms. Each of the prisoners is offered the following options: 1)如果一人认罪，另一个不认罪，认罪的人会被释放，不认罪的人将被判20年徒刑。 2)如果两人都认罪，每人判5年徒刑。 3)如果两人都不认罪，每人判1年徒刑。,Bonnie And Clyde,Bonnie And Clyde,Each of the prisoners is offered the following options: 1)如果一人认罪，另一个不认罪，认罪的人会被释放，不认

46、罪的人将被判20年徒刑。 2)如果两人都认罪，每人判5年徒刑。 3)如果两人都不认罪，每人判1年的徒刑.,Why Both Confess,如果两人在被捕后能够相互之间沟通并达成共谋，他们就会都承担较轻的惩罚。 但是在没有共谋的前提下，每一个嫌疑人都面临着巨大的坦白的压力，因为如果自己不坦白而另一方坦白，自己就面临最严厉的惩罚。,In The Absence Of Collusion,通常的情况下是双方都坦白，从而都面临中间状态的惩罚。 这是因为逃脱囚犯困境的唯一办法是信任，但是信任是非常难以形成的，除非他们之间存在显性的遵从信任的约束机制。,Duopoly,双寡头垄断市场可以存在于那些最小效

47、率规模正好是市场总需求量的一半的市场上。,我们可以把囚犯困境理论应用于对双寡头垄断的市场的分析。,Duopoly,Duopoly,What is the likely strategic pricing decision to be, how much will each produce, and what will be their total economic profits? （没有共谋） a) Price will be set at $500, each will produce 4000 tons, and economic profits will be zero. b) Pri

48、ce will be set at $600, each will produce 3000 tons, and economic profits will be $75,000 per firm. c) Im still thinking about that trip to Vegas.,Quantity,Price,MC,ATC,A,4000,500,S=MC,D,8000,MR,600,6000,Price,Quantity,575,ATC,What is the likely strategic pricing decision to be, how much will each p

49、roduce, and what will be their total economic profits? a) Price will be set at $500, each will produce 4000 tons, and economic profits will be zero. b) Price will be set at $600, each will produce 3000 tons, and economic profits will be $75,000 per firm. c) Im still thinking about that trip to Vegas

50、.,Quantity,Price,MC,ATC,A,4000,500,S=MC,D,8000,MR,600,6000,Price,Quantity,575,ATC,What is the likely market price, output, and profit and which of the three traditional oligopoly models does this outcome most resemble?（存在共谋） a) Price will be set at $500, each will produce 4000 tons, and economic pro

51、fits will be zero. This resembles the kinked demand model. b) Price will be set at $600, each will produce 3000 tons, and economic profits will be $75,000 per firm. This resembles the cartel or joint profit maximization model. c) Ive stopped thinking about my trip to Vegas but now must confront the

52、bleak possibility that I will get this question wrong and never become a titan of industry.,Quantity,Price,MC,ATC,A,4000,500,S=MC,D,8000,MR,600,6000,Price,Quantity,575,ATC,What is the likely market price, output, and profit and which of the three traditional oligopoly models does this outcome most r

53、esemble? a) Price will be set at $500, each will produce 4000 tons, and economic profits will be zero. This resembles the kinked demand model. b) Price will be set at $600, each will produce 3000 tons, and economic profits will be $75,000 per firm. This resembles the cartel or joint profit maximizat

54、ion model. c) Ive stopped thinking about my trip to Vegas but now must confront the bleak possibility that I will get this question wrong and never become a titan of industry.,Quantity,Price,MC,ATC,A,4000,500,S=MC,D,8000,MR,600,6000,Price,Quantity,575,ATC,600,575,3000,现在我们考虑达成共谋的双方中的一方是一个暗箭伤人的人，他决定欺

55、骗对方，私下将自己的产量增加到4000。,Quantity,Price,MC,ATC,A,4000,500,S=MC,D,8000,MR,600,6000,Price,Quantity,575,ATC,7000,550,What happens now to the market price, output, and profit? a) Price falls to $550, industry output increases to 7000 tons, the non-cheating firm loses $75,000, and the cheating duopoly makes

56、a $200,000 economic profit. b) Price falls to $500, industry output increases to 8000 tons, and both firms earn zero economic profits. c) The CEO of the non-cheating firm starts listening to country music and his favorite song becomes “Your Cheating Heart.”,550,575,Quantity,Price,MC,ATC,A,4000,500,S

57、=MC,D,8000,MR,600,6000,Price,Quantity,575,ATC,7000,550,What happens now to the market price, output, and profit? a) Price falls to $550, industry output increases to 7000 tons, the non-cheating firm loses $75,000, and the cheating duopoly makes a $200,000 economic profit. b) Price falls to $500, ind

58、ustry output increases to 8000 tons, and both firms earn zero economic profits. c) The CEO of the non-cheating firm starts listening to country music and his favorite song becomes “Your Cheating Heart.”,3000,550,575,3000,Quantity,Price,MC,ATC,A,4000,500,S=MC,D,8000,MR,600,6000,Price,Quantity,575,ATC

59、,7000,550,这个例子说明存在着对双寡头垄断厂商欺骗对方的利益激励。 In this case, the successful cheater can more than double his profits from $75,000 to $200,000.,基本概念 策略和报酬 支付矩阵（报酬矩阵） 博弈均衡 纳什均衡 静态博弈与动态博弈（重复博弈）,博弈论初步,乙,石头 剪刀 布,石头 剪刀 布,甲,0 ，0,1 ，-1,-1 ， 1,-1 ，1,0 ， 0,1 ，-1,1 ，-1,-1 ， 1,0 ，0,1、博弈描述 游戏石头、剪刀、布,2、博弈模型的3个基本要素,（1）游戏者（player）指博弈中的每个决策者 。以自