寡头数量如何影响市场结果 How the Size of an Oligopoly 博弈论与合作经济学 Affects the market outcome Game Theory and the Economics of Cooperation 随着寡头市场上卖者数目的增加,寡头市场越来 越象竞争市场。 ◆博弈论是研究人们在各种战略情况下如何行事 As the number of sellers in an oligopoly grows Game theory is the study of how people behave in larger, an oligopolistic market looks more and more strategic situatio like a competitive market. 战略决策指的是每个人在决定采取什么行动时,必 ◆价格趋近于边际成本,生产量趋近于社会有效率 须考虑其他人对这种行动作出什么反应的状况 的水平。 Strategic decisions are those in which each person, in The price approaches marginal cost, and the deciding what actions to take, must consider how quantity produced approaches the socially efficient others might respond to that action 博弈论与合作经济学 Game Theory and the 纳什均衡 Economics of Cooperation Nash Equilibrium ◆由于在寡头市场中企业的数目很少,因此每家 H什均衡是指这样的情况:相互作用中的 Because the number of firms in an oligopolistic 每一个经济人,在其他方所选择的战略为 market is small. each firm must act 既定时,选择了自己的最优战略。 strategically A Nash equilibrium is a situation in which ◆每个企业都知道 润不仅取决它生产多 economic actors interacting with one 少,而且还取决 another each choose their best strategy Each firm knows that its profit depends not only on how much it produced but also on how given the strategies that all the others have much the other firms produce. chosen 纳什均衡 囚犯的两难处境 Nash Equilibrium The Prisoners'Dilemma 囚犯的两难处境表明了维持合作的困难 正如市场均衡( Market Equilibrium)代 The prisoners'dilemma provides insight 表着经济学家对竞争性市场下人们相互作 into the difficulty in maintaining 用结果的一种预测,纳什均衡代表着他们 cooperation 对战略决策的情形下人们相互作用结果的 人们(企业)经常不能互相合作,尽管 种预测 合作可以使他们都收益 Often people(firms)fail to cooperate with one another even when cooperation would make them better off.4 19 寡头数量如何影响市场结果 How the Size of an Oligopoly Affects the Market Outcome ‹随着寡头市场上卖者数目的增加，寡头市场越来 越象竞争市场。 As the number of sellers in an oligopoly grows larger, an oligopolistic market looks more and more like a competitive market. ‹价格趋近于边际成本，生产量趋近于社会有效率 的水平。 The price approaches marginal cost, and the quantity produced approaches the socially efficient level. 20 博弈论与合作经济学 Game Theory and the Economics of Cooperation ‹博弈论是研究人们在各种战略情况下如何行事。 Game theory is the study of how people behave in strategic situations. ‹战略决策指的是每个人在决定采取什么行动时，必 须考虑其他人对这种行动作出什么反应的状况。 Strategic decisions are those in which each person, in deciding what actions to take, must consider how others might respond to that action. 21 博弈论与合作经济学 Game Theory and the Economics of Cooperation ‹由于在寡头市场中企业的数目很少，因此每家 企业都必须按战略行事。 Because the number of firms in an oligopolistic market is small, each firm must act strategically. ‹每个企业都知道，它的利润不仅取决它生产多 少，而且还取决于其他企业生产多少。 Each firm knows that its profit depends not only on how much it produced but also on how much the other firms produce. 22 纳什均衡 Nash Equilibrium 纳什均衡是指这样的情况：相互作用中的 每一个经济人，在其他方所选择的战略为 既定时，选择了自己的最优战略。 A Nash equilibrium 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. 23 纳什均衡 Nash Equilibrium 正如市场均衡（Market Equilibrium）代 表着经济学家对竞争性市场下人们相互作 用结果的一种预测，纳什均衡代表着他们 对战略决策的情形下人们相互作用结果的 一种预测。 24 囚犯的两难处境 The Prisoners’ Dilemma 囚犯的两难处境表明了维持合作的困难 The prisoners’ dilemma provides insight into the difficulty in maintaining cooperation. 人们（企业）经常不能互相合作，尽管 合作可以使他们都收益 Often people (firms) fail to cooperate with one another even when cooperation would make them better off