最新微观经济学16寡头垄断PPT课件.ppt

微观经济学微观经济学1616寡头垄断寡头垄断•Imperfect competition refers to those market structures that fall between perfect competition and pure monopoly.•Imperfect competition includes industries in which firms have competitors but do not face so much competition that they are price taker.Between Monopoly and Perfect competition•A duopoly is an oligopoly with two members. It is the simplest type of oligopoly.16.2.1 A Duopoly Example•Price and Quantity Supplied•The price of water in a perfectly competitive market would be driven to where the marginal cost is zero:•P = MC = $0•Q = 120 gallons•The price and quantity in a monopoly market would be where total profit is maximized:•P = $60•Q = 60 gallons16.2.1 A Duopoly Example•Price and Quantity Supplied•The socially efficient quantity of water is 120 gallons, but a monopolist would produce only 60 gallons of water:•So what outcome then could be expected from duopolists?16.2.1 A Duopoly Example•The duopolists may agree on a monopoly outcome.• Collusion合谋合谋•An agreement among firms in a market about quantities to produce or prices to charge.• Cartel卡特尔卡特尔•A group of firms acting in unison.16.2.2 Competition, Monopolies, and Cartels•Although oligopolists would like to form cartels and earn monopoly profits, often that is not possible. Antitrust laws prohibit explicit agreement among oligopolists as matter of public policy. 16.2.2 Competition, Monopolies, and Cartels•A Nash equilibrium(纳什均衡纳什均衡) is a situation in which economic actors interacting with one another each choose their best strategy given the strategies that all the others have chosen. 16.2.3 The Equilibrium for an Oligopoly •When firms in an oligopoly individually choose production to maximize profit, they produce quantity of output greater than the level produced by monopoly and less than the level produced by competition.•The oligopoly price is less than the monopoly price but greater than the competitive price (which equals marginal cost).16.2.3 The Equilibrium for an Oligopoly ØPossible outcome if oligopoly firms pursue their own self-interests:•Joint output is greater than the monopoly quantity but less than the competitive industry quantity.•Market price are lower than the monopoly price but greater than the competitive industry price.•Total profits are less than the monopoly profit. 16.2.3 Equilibrium for an Oligopoly 16.2.4 How the Size of an Oligopoly Affects the Market OutcomeHow increasing the number of sellers affects the price and quantity:•The output effect: Because price is above marginal cost, selling more at the going price raises profits. (First it sells more output and receives a revenue of py from that.)•The price effect: Raising production will increase the amount sold, which will lower the price and the profit per unit on all units sold. (second, the monopolist, pushes the price down by p and it gets this lower price on all the output it has been selling.)r = p y + y p16.2.4 How the Size of an Oligopoly Affects the Market Outcome•As the number of sellers in an oligopoly grows larger, an oligopolistic market looks more and more like a competitive market.•The price approaches marginal cost, and the quantity produced approaches the socially efficient level.16.3 Game Theory and The Economics Of Cooperation• Game theory is the study of how people behave in strategic situations.•“Strategic” decisions are those in which each person, in deciding what actions to take, must consider how others might respond to that action.•Because the number of firms in an oligopolistic market is small, each firm must act strategically.•Each firm knows that its profit depends not only on how much it produces but also on how much the other firms produce.16.3 Game Theory and The Economics Of Cooperation•Game theory is not necessary for understanding competitive or monopoly markets. 1)In a competitive market, each firm is so small compared to the market that strategic interactions with other firms are not important. 2)In a monopolized market, strategic interactions are absent because the market has only one firm. But game theory is quite useful for understanding the behavior of oligopolies.16.3.1 The Prisoner’s Dilemma•A particularly important “game” is called the prisoners’ dilemma. The prisoner’s dilemma provides insight into the difficulty in maintaining cooperation. •Many times in life, people(firms) fail to cooperate with one another even when cooperation would make them better off.Figure 2 The Prisoners’ DilemmaCopyright©2003 Southwestern/Thomson LearningBonnie’ s DecisionConfessConfessBonnie gets 8 yearsClyde gets 8 yearsBonnie gets 20 yearsClyde goes freeBonnie goes freeClyde gets 20 yearsgets 1 yearBonnie Clyde gets 1 yearRemain SilentRemainSilentClyde’sDecision•The prisoner’s dilemma is a particular “game” between two captured prisoners that illustrates why cooperation is difficult to maintain even when it is mutually beneficial.(Mankiw, 3th edition, p355-356.)•Let’s call them Bonnie and Clyde. The police have enough evidence to convict Bonnie and Clyde of the minor crime of carrying an unregistered gun, so that each would spend a year in jail. The police also suspect that the two criminals have committed a bank robbery together, but they lack hard evidence to convict them of this major crime. The police question Bonnie and Clyde in separate rooms, and they offer each of them the following deal:•“Right now, we can lock you up for 1 year. If you confess to the bank robbery and implicate涉及 your partner, however, we’ll give you immunity and you can go free. Your partner will get 20 years in jail. But if you both confess to the crime, we won’t need your testimony and we can avoid the cost of a trial, so you will each get an intermediate sentence of 8 years. ”•If Bonnie and Clyde, heartless bank robbers that they are, care only about their own sentences, what would you expect them to do? Would they confess or remain silent? Figure 2 shows their choices. Each prisoner has two strategies: confess or remain silent. The sentence each prisoner gets depends on the strategy he or she chooses and the strategy chosen by his or her partner in crime.•Consider first Bonnie’s decision. She reasons as follows:”I don’t know what Clyde is going to do. If he remains silent, my best strategy is to confess, since then I’ll go free rather than spending a year in jail. If he confesses, my best strategy is still to confess, since then I’ll spend 8 years in jail rather than 20. So, regardless of what Clyde does, I am better off confessing.”•In the language of game theory, a strategy is called a dominant strategy if it is the best strategy for a player to follow regardless of the strategies pursued by other players. In this case, confessing is a dominant strategy for Bonnie, She spends less time in jail if she confesses, regardless of whether Clyde confesses or remains silent.•Now consider Clyde’s decision. He faces exactly the same choices as Bonnie, and he reasons in much the same way. Regardless of what Bonnie does, Clyde can reduce his time in jail by confessing. In other words, confessing is also a dominant strategy for Clyde.•In the end, both Bonnie and Clyde confess, and both spend 8 years in jail. Yet, from their standpoint, this is a terrible outcome. If they had both remained silent, both of them would have been better off, spending only 1 year in jail on the gun charge. By each pursuing his or her own interests. The two prisoners together reach an outcome that is worse for each of them.16.3.1 The Prisoner’s Dilemma•The dominant strategy is the best strategy for a player to follow regardless of the strategies chosen by the other players.•Cooperation is difficult to maintain, because cooperation is not in the best interest of the individual player.16.3.1 The Prisoner’s Dilemma•There are two players. Both can choose between cooperating( C ) and finking (F). 1)If they both cooperate. They both obtain 3. 2)If they both fink, they both obtain 0. 3)If one cooperates and the other finks, they get –1 and 4, respectively. •In the one-shot version of this game, finking is a dominant strategy for both players. That is , each player gains from finking, regardless of the other player’s choice. Hence, the only Nash equilibrium is (F, F).(Jean Tirole, The Theory of Industrial Organization, chapter6, p258.)•Fink: n. 向警方通报罪犯情况的人Player 1Player 2CooperatingCooperatingFinkingFinking33- 14- 1400The Prisoner’s DilemmaFigure 3 An Oligopoly GameCopyright©2003 Southwestern/Thomson LearningIraq’s DecisionHigh ProductionHigh ProductionIraq gets $40 billionIran gets $40 billionIraq gets $30 billionIran gets $60 billionIraq gets $60 billionIran gets $30 billionIraq gets $50 billionIran gets $50 billionLow ProductionLowProductionIran’sDecision•Consider an oligopoly with two members, called Iran and Iraq. Both countries sell crude oil. After prolonged negotiation, the countries agree to keep oil production low in order to keep the world price of oil high. After they agree on production levels, each country must decide whether to cooperate and live up to this agreement or to ignore it and produce at a higher level. Figure 3 shows how the profits of the two countries depend on the strategies they choose.16.3.2 Oligopolies as a Prisoner’s Dilemma•Suppose you are the president of Iraq. You might reason as follows: “I could keep production low as we agreed, or I could raise my production and sell more oil on world markets. If Iran lives up to the agreement and keeps its production low, then my country earns profit of $60 billion with high production and $50 billion with low production. In this case, Iraq is better off with high production. If Iran fails to live up to the agreement and produces at a high level, then my country earns $40 billion with high production and $30 billion with low production. Once again, Iraq is better off with high production. So, regardless of what Iran chooses to do, my country is better off reneging on our agreement and producing at a high level.”16.3.2 Oligopolies as a Prisoner’s Dilemma•Producing at a high level is a dominant strategy for Iraq. Of course, Iran reasons in exactly the same way, and so both countries produce at a high level. The result is the inferior outcome with low profits for each country.•This example illustrates why oligopolies have trouble maintaining monopoly profits. The monopoly outcome is jointly rational for the oligopoly, but each oligopolist has an incentive to cheat. Self-interest makes it difficult for the oligopoly to maintain a cooperative outcome with low production, high prices, and monopoly profits.16.3.2 Oligopolies as a Prisoner’s DilemmaFigure 4 An Arms-Race GameCopyright©2003 Southwestern/Thomson LearningDecision of the United States (U.S.)ArmArmU.S. at riskUSSR at riskU.S. at risk and weakUSSR safe and powerfulU.S. safe and powerfulUSSR at risk and weakU.S. safeUSSR safeDisarmDisarmDecision of the Soviet Union (USSR)•When two firms advertise to attract the same customers, they face a problem similar to the prisoners’ dilemma. For example, consider the decisions facing two cigarette companies, Marlboro and Camel. If neither company advertises, the two companies split the market. If both advertise, they again split the market, but profits are lower, since each company must bear the cost of advertising. Yet if one company advertises while the other does not, the one that advertises attracts customers from the other. AdvertisingFigure 5 An Advertising GameCopyright©2003 Southwestern/Thomson LearningMarlboro’ s Decision AdvertiseAdvertiseMarlboro gets $3billion profitCamel gets $3billion profitCamel gets $5billion profitMarlboro gets $2billion profitCamel gets $2billion profitMarlboro gets $5billion profitCamel gets $4billion profitMarlboro gets $4billion profitDon’t AdvertiseDon’tAdvertiseCamel’sDecision•Figure 5 shows how the profits of the two companies depend on their actions. You can see that advertising is a dominant strategy for each firm. Thus, both firms choose to advertise, even though both firms would be better off if neither firm advertised.•A test of this theory of advertising occurred in 1971, when Congress passed a law banning cigarette advertisements on television. To the surprise of many observers, cigarette companies did not use their considerable political clout to oppose the law. When the law went into effect, cigarette advertising fell, and the profits of cigarette companies rose. The law did for the cigarette companies what they could not do on their own: It solved the prisoners’ dilemma by enforcing the cooperative outcome with low advertising and high profit.Figure 6 A Common-Resource GameCopyright©2003 Southwestern/Thomson LearningExxon’s Decision Drill TwoWellsDrill Two WellsExxon gets $4million profitTexaco gets $4million profitTexaco gets $6million profitExxon gets $3million profitTexaco gets $3million profitExxon gets $6million profitTexaco gets $5million profitExxon gets $5million profitDrill One WellDrill OneWellTexaco’sDecision16.3.4 Prisoners’ Dilemma and the Welfare of Society1.In some cases, the noncooperative equilibrium is bad for society as well as the players. In the arms-race game in Figure 4, both the U.S. and the Soviet Union end up at risk. In the common-resources game in Figure 6, the extra wells dug by Texaco and Exxon are pure waste. In both cases, society would be better off if the two players could reach the cooperative outcome.1.By contrast, in the case of oligopolists trying to maintain monopoly profits, lack of cooperation is desirable from the standpoint of society as a whole. The monopoly outcome is good for the oligopolists, but it is bad for the consumers of the product. The competitive outcome is best for society because it maximizes total surplus. When oligopolists fail to cooperate, the quantity they produce is closer to this optimal level. Put differently, the invisible hand guides markets to allocate resources efficiently only when markets are competitive, and markets are competitive only when firms in the market fail to cooperate with one another.16.3.4Prisoners’ Dilemma and the Welfare of Society2.Similarly, consider the case of the police questioning two suspects. Lack of cooperation between the suspects is desirable, for it allows the police to convict more criminals. The prisoners’ dilemma is a dilemma for the prisoners, but it can be a boon to everyone else.•Boon: n. thing that one is thankful for, benefit, advantage所感激的事，利益，好处；•Boon:adv. (idm) a boon companion好友16.3.5 Why People Sometimes CooperateFirms that care about future profits will cooperate in repeated games rather than cheating in a single game to achieve a one-time gain.The threat of this penalty may be all that is needed to maintain cooperation. Each person knows that defecting would raise his profit form $1800 to $2000. But this benefit would last for only one week. Thereafter, profit would fall to $1600 and stay there. As long as the players care enough about future profits, they will choose to forgo the one-time gain from defection. Thus, in a game of repeated prisoners’ dilemma, the two players may well be able to reach the cooperative outcome.Figure 7 Jack and Jill Oligopoly GameCopyright©2003 Southwestern/Thomson LearningJack’s Decision Sell 40GallonsSell 40 GallonsJack gets$1,600 profitJill gets$1,600 profitJill gets$2,000 profitJack gets$1,500 profitJill gets$1,500 profitJack gets$2,000 profitJill gets$1,800 profitJack gets$1,800 profitSell 30 GallonsSell 30GallonsJill’sDecision16.4 Public Policy Toward Oligopolies•Cooperation among oligopolists is undesirable from the standpoint of society as a whole because it leads to production that is too low and prices that are too high.•Antitrust laws make it illegal to restraint trade or attempt to monopolize a market.•Sherman Antitrust Act of 1890•Clayton Act of 191416.4.1 Restraint of trade and the Antitrust Laws•Antitrust policies sometimes may not allow business practices that have a potentially positive effects:•Resale price maintenance转售价格控制转售价格控制•Predatory pricing•Tying16.4.2 Controversies over Antitrust Policy•Resale price maintenance (or fair trade)•occurs when supplies (like wholesalers) require retailers to charge a specific amount•Predatory Pricing•occurs when a large firm begins to cut the price of its product(s) with the intent of driving its competitor(s) out of the market•Tying •when a firm offers two (or more) of its products together at a single price, rather than separately16.4.2 Controversies over Antitrust PolicyAppendix: Ignoring Interdependencies: The Cournot Oligopoly•Models vary depending on assumptions of actions of rivals to pricing and output decisions.•Augustin Cournot (1838) created a model that is the basis of Anti-trust Policy in the US.–Relatively simple assumption: ignore the interdependency with rivals–This makes the math easyCournotA Numerical Example:Competition, Monopoly, and Cournot Oligopoly•IN COMPETITION–P = MC, so 950 - Q = 50–PC = $50 and QM = 900•IN MONOPOLY–MR = MC, so 950 -2Q = 50–QM = 450 so–PM = 950 - 450 = $500•IN DUOPOLY–Let Q = q1 + q2DPMPcournotPC QM QCournot QC 450 600 900$500$350$50Let: P = 950 - Q and MC =50Cournot Solution: Case of 2 Firms (Duopoly) •Assume each firm maximizes profit•Assume each firm believes the other will NOT change output as they change output.–The so-called: Cournot Assumption•Find where each firm sets MR = MCLet Q = q1 + q2lP = 950 - Q = 950 - q1- q2 and MC = 50lTR1 = Pq1= (950- q1-q2)q1 =950q1 - q12 - q1q2 andlTR2 = Pq2= (950- q1-q2)q2 =950q2 - q2q1 - q22 lSet MR1= MC & MR2= MC950 -2q1 - q2 = 50950 - q1 - 2q2 = 502 equations &2 unknownsWith 2 Equations & 2 Unknowns: Solve for Output950 -2q1 - q2 = 950 - q1 - 2q2 So, q2 = q1 Then plug this into the demand equation we find:950 - 2q1 - q1 = 950 - 3q1 = 50.Therefore q1 = 300 and Q = 600The price is: P = 950 - 600 = $350P QCompetition 50 900Cournot 350 600Monopoly 500 450Cournot’sanswer isbetween theother two.Case: Cournot Solution: 西门子公司与汤姆森西门子公司与汤姆森-CSF公司公司假设两家欧洲电子公司西门子(厂商S)和汤姆森-CSF(厂商T)共同持有一项用于机场雷达系统的零件的专利权.(13-1)(13-3)(13-2)N-Firm Cournot Model•For 3 firms with linear demand and cost functions:–Q = q 1 + q 2 + q 3–In linear demand and cost models, the solution is higher output and lower priceQCournot = { N / (N+1) }QCompetitionQCNNPCTHEREFORE, Increasing the Number of Firms increases competition. This is the historical basis for Anti-trust PoliciesExample: Cournot as N Increases•If N = 3 Triopoly•P = 950 - Q & MC=50•Then, Q = (3/4)(900)•Q = 675•P =$275•If N = 5•P = 950 - Q and MC = 50•Then Q = (5/6)(900)•Q = 750•P = $200N = 3 N = 5Appendix: Collusion versus Competition?•Sometimes collusion succeeds•Sometimes forces of competition win out over collective action•When will collusion tend to succeed?–There are six factors that influence successful collusion as follows: Factors Affecting Likelihood of Successful Collusion1.Number and Size Distribution of Sellers. Collusion is more successful with few firms or if there exists a dominant firm. 2.Product Heterogeneity. Collusion is more successful with products that are standardized or homogeneous3.Cost Structures. Collusion is more successful when the costs are similar for all of the firms in the oligopoly.4.Size and Frequency of Orders. Collusion is more successful with small, frequent orders.5.Secrecy and Retaliation. Collusion is more successful when it is difficult to give secret price concessions. 6.Percentage of External Orders. Collusion is more successful when percentage of orders outside of the cartel is small.Appendix: Quantity Competition; An Example•Suppose that the market inverse demand function isand that the firms’ total cost functions areandQuantity Competition; An ExampleThen, for given y2, firm 1’s profit function isSo, given y2, firm 1’s profit-maximizingoutput level solvesQuantity Competition; An ExampleThen, for given y2, firm 1’s profit function isSo, given y2, firm 1’s profit-maximizingoutput level solvesI.e. firm 1’s best response to y2 isQuantity Competition; An Exampley2y16015Firm 1’s “reaction curve”Quantity Competition; An ExampleSimilarly, given y1, firm 2’s profit function isSo, given y1, firm 2’s profit-maximizingoutput level solvesI.e. firm 2’s best response to y1 isQuantity Competition; An Exampley2y1Firm 2’s “reaction curve”45/445Quantity Competition; An Example•An equilibrium is when each firm’s output level is a best response to the other firm’s output level, for then neither wants to deviate from its output level.•A pair of output levels (y1*,y2*) is a Cournot-Nash equilibrium if andQuantity Competition; An ExampleandQuantity Competition; An ExampleandSubstitute for y2* to getHenceSo the Cournot-Nash equilibrium isQuantity Competition; An Exampley2y1Firm 2’s “reaction curve”6015Firm 1’s “reaction curve”45/445Quantity Competition; An Exampley2y1Firm 2’s “reaction curve”4860Firm 1’s “reaction curve”813Cournot-Nash equilibrium16. Kinked Oligopoly Demand Curve如果一个寡头厂商削减其价格如果一个寡头厂商削减其价格,竞争者将很快感觉到他们竞争者将很快感觉到他们的销售量在下降的销售量在下降,并且不得不相应降低价格；相反并且不得不相应降低价格；相反,如果一如果一个寡头厂商提高其价格个寡头厂商提高其价格,竞争者就会通过保持其原价不变竞争者就会通过保持其原价不变而迅速赢得消费者而迅速赢得消费者,因此缺乏或没有随之提高价格的积极因此缺乏或没有随之提高价格的积极性性。

在这种情况下,单个寡头厂商提高其价格而其他公司并不跟随提价,那么价格的提高将导致提价厂商市场份额的下降,这种情况如图13-6所示需求曲线上的KD‘ 部分就是市场份额需求曲线,在此范围内所有的竞争对手都会相应同样地调整价格,此厂商的市场份额保持不变.当价格提高到P之上,若竞争对手不做相应调整,那么提价厂商面对的需求曲线弹性更为充足.价格增加,其市场份额下降16. Kinked Oligopoly Demand Curve寡头厂商的需求曲线由DKD‘ 表示的,市场通行价格为P，产量为Q由于需求曲线在K处弯折,所以边际收益曲线是不连续的边际收益曲线要用两条直线来表示，即MRX和MR’Y如果边际成本曲线如果边际成本曲线MC穿过边际收益曲线上的穿过边际收益曲线上的缺口缺口XY,那么利润最大化的选择就是保持目前的价格与产那么利润最大化的选择就是保持目前的价格与产量的政策对于那些认为自己面对一条弯折需求曲线的量的政策对于那些认为自己面对一条弯折需求曲线的厂商来说厂商来说,即使成本可能在相当大的范围内变化即使成本可能在相当大的范围内变化(如如MC2和和MC1),利润最大化的价格和产量水平也会保持不变利润最大化的价格和产量水平也会保持不变。

同样,需求曲线不管是向右移动(需求增加),还是向左移动(需求减少),都可能不会改变厂商的价格决策因为需求曲线的弯折点是由通行价格决定的,所以需求曲线的移动也会使边际收益曲线的缺口XY左右移动.如果MC仍从缺口穿过,尽管产量会增加或减少,但通行价格不变Figure 12.8Summary•Oligopolists maximize their total profits by forming a cartel and acting like a monopolist.•If oligopolists make decisions about production levels individually, the result is a greater quantity and a lower price than under the monopoly outcome.Summary•The prisoner’s dilemma shows that self-interest can prevent people from maintaining cooperation, even when cooperation is in their natural self-interest.•The logic of the prisoners’ dilemma applies in many situations, including oligopoies. Summary•Policymakers use the antitrust laws to prevent oligopolies from engaging in behavior that reduces competition. Mankiw, chapter16-queation5, p370.5. Consider trade relations between the U.S. and Mexico. Assume that the leaders of the two countries believe the payoffs to alternative trade policies are as follows:Mexico’sdecisionUnited States’ decisionLow tariffsMexico gains$25 billionHigh tariffsLowtariffsHightariffsU.S. gains$25 billionU.S. gains$30 billionU.S. gains$10 billionU.S. gains$20 billionMexico gains$10 billionMexico gains$30 billionMexico gains$20 billiona.What is the dominant strategy for the United States? For Mexico? Explain.b.Define Nash Equilibrium. What is the Nash equilibrium for trade policy?c.In 1993 the U.S. Congress ratified the North American Free Trade Agreement (NAFTA), in which the U.S. and Mexico agreed to reduce trade barriers simultaneously. Do the perceived payoffs shown here justify this approach to trade policy?。