清华大学：经济学原理：Ch_16

1 寡头 Oligopoly 第16章 Chapter 16 2 不完全竞争 Imperfect Competition 不完全竞争指的是介于完全竞争 和纯垄断之间的那些市场结构。 Imperfect competition refers to those market structures that fall between perfect competition and pure monopoly. 3 不完全竞争 Imperfect Competition 不完全竞争包括这样的产业：企 业面临竞争，但竞争没有激烈到 使企业成为价格接受者。 Imperfect competition includes industries in which firms have competitors but do not face so much competition that they are price takers. 4 不完全竞争市场的类型 Types of Imperfectly Competitive Markets ?寡头Oligopoly ?只有少数几个卖者，每个卖者提供与其他企 业相似或相同的产品。 Only a few sellers, each offering a similar or identical product to the others. ?垄断竞争Monopolistic Competition ?一个有许多出售相似但不相同的产品的企业 的市场结构。 Many firms selling products that are similar but not identical. 5 市场结构的四种类型 The Four Types of Market Structure 垄断 Monopoly 寡头 Oligopoly 垄断竞争 Monopolistic Competition 完全竞争 Perfect Competition ?自来水 Tap water ?有线电视 Cable TV ?网球 Tennis balls ?原油 Crude oil ?小说 Novels ?电影 Movies ?小麦 Wheat ?牛奶 Milk 企业数量Number of Firms? 产品类型 Type of Products? 许多 Many firms 一家 One firm 几家 Few firms 有差别产品 Differentiated products 相同产品 Identical products 6 只有少数几个卖者的市场 Markets With Only a Few Sellers 由于只有少数几个卖者，寡头 市场的关键特征是合作与利己 之间的冲突。 Because of the few sellers, the key feature of oligopoly is the tension between cooperation and self-interest. 2 7 寡头市场的特征 Characteristics of an Oligopoly Market ?少数几个卖者提供相似或相同的产品 Few sellers offering similar or identical products ?相互关联的企业 Interdependent firms ?最好是合作，象垄断那样生产少量产品并把价 格定在边际成本之上 Best off cooperating and acting like a monopolist by producing a small quantity of output and charging a price above marginal cost 8 双头的例子 A Duopoly Example 双头是只有两个卖者的寡头。 双头是最简单的寡头模型。 A duopoly is an oligopoly with only two members. It is the simplest type of oligopoly. 9 双头的例子：水的需求表 A Duopoly Example: Demand Schedule for Water Quantity Price Total Revenue 0 $120 $ 0 10 110 1,100 20 100 2,000 30 90 2,700 40 80 3,200 50 70 3,500 60 60 3,600 70 50 3,500 80 40 3,200 90 30 2,700 100 20 2,000 110 10 1,100 120 0 0 10 双头的例子：价格和供给量 A Duopoly Example: Price and Quantity Supplied ?在完全竞争的市场中，水的价格等于边际成本即零 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 ?在垄断的市场中，价格和数量使垄断者的总利润最 大化。The price and quantity in a monopoly market would be where total profit is maximized: P = $60 Q = 60 gallons 11 双头的例子：价格和供给量 A Duopoly Example: Price and Quantity Supplied ?社会有效率的水的供应量是120加仑，但垄断 者只供应60加仑。 The socially efficient quantity of water is 120 gallons, but a monopolist would produce only 60 gallons of water. ?我们预期双头是什么结果呢? So what outcome then could be expected from duopolists? 12 竞争、垄断和卡特尔 Competition, Monopolies, and Cartels ?双头可以同意垄断的结果。 The duopolists may agree on a monopoly outcome. ?勾结Collusion ?两个企业就生产的数量和收取的价格达成一致 The two firms may agree on the quantity to produce and the price to charge. ?卡特尔Cartel ?两个企业联合起来，协调行动。 The two firms may join together and act in unison. 3 13 竞争、垄断和卡特尔 Competition, Monopolies, and Cartels 尽管寡头希望形成卡特尔并赚到垄断利润，但 这往往是不可能的。 Although oligopolists would like to form cartels and earn monopoly profits, often that is not possible. 反托拉斯法把禁止寡头之间的公开协议作为公 共政策的重点。 Antitrust laws prohibit explicit agreements among oligopolists as a matter of public policy. 14 寡头的均衡 The Equilibrium for an Oligopoly 9003060 1,20040(30)50 1,6004040 2,00050(40)30 2,5005020 3,00060(50)10 3,600600 （吉尔） 并获得利 润…… 吉尔最优 的产量选 择是…… 给定杰克 选择产量 为…… Quantity Price Total Revenue 0 $120 $ 0 10 110 1,100 20 100 2,000 30 90 2,700 40 80 3,200 50 70 3,500 60 60 3,600 70 50 3,500 80 40 3,200 90 30 2,700 100 20 2,000 110 10 1,100 120 0 0 寡头的均衡结果 15 寡头的均衡 The Equilibrium for an Oligopoly Quantity Price Total Revenue 0 $120 $ 0 10 110 1,100 20 100 2,000 30 90 2,700 40 80 3,200 50 70 3,500 60 60 3,600 70 50 3,500 80 40 3,200 90 30 2,700 100 20 2,000 110 10 1,100 120 0 0竞争的市场结果 寡头的市场结果 垄断的市场结果 16 寡头的均衡 Equilibrium for an Oligopoly ?如果寡头企业各自追求自己的利益，可能的结 果是：Possible outcome if oligopoly firms pursue their own self-interests: ?总产量大于垄断产量但小于竞争产量 Joint output is greater than the monopoly quantity but less than the competitive industry quantity. ?市场价格低于垄断价格但高于竞争价格 Market prices are lower than monopoly price but greater than competitive price. ?总利润小于垄断利润 Total profits are less than the monopoly profit. 17 寡头数量如何影响市场结果 How the Size of an Oligopoly Affects the Market Outcome ?（与垄断时类似）在做出增加或者减少产量的 边际决策时，每个卖者都要考虑两种效应： In making the marginal decision on increasing/decreasing one unit of its production, each seller weighs two effects: ?产量效应：由于价格高于边际成本，在现行价格上 多销售将增加利润。 The output effect: Because price is above marginal cost, selling more at the going price raises profits. ?价格效应：提高生产将增加总销售量，这会降低价 格并减少所有销售量每一单位的利润。 The price effect: Raising production lowers the price and the profit per unit on all units sold. 18 寡头数量如何影响市场结果 How the Size of an Oligopoly Affects the Market Outcome ?卖者数目的增加如何影响这两种效应 How increasing the number of sellers affects these two effects: ?随着寡头数量增加，价格效应在减少。 As the oligopoly grows in size, the magnitude of the price effect falls. ?当寡头数量增加到极大时，价格效应几乎消失，只 剩下了产量效应。 When the oligopoly grows very large, the price effect disappear altogether, leaving only the output effect. 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. 5 25 囚犯的两难处境 The Prisoners’ Dilemma 波宁的决策 Bonnie’s Decision 坦白Confess保持沉默Remain Silent 坦白Confess 保持沉默 Remain Silent 克莱德的 决策 Clyde’s Decision Clyde gets 8 years 克莱德入狱8年 Bonnie gets 8 years 波宁入狱 8年 Bonnie gets 20 years 波宁入狱 20年 Bonnie gets 1 year 波宁入狱 1年 Bonnie goes free 波宁自由 Clyde gets 20 years 克莱德入狱20年 Clyde gets 1 year 克莱德入狱1 年 Clyde goes Free 克莱德自由 26 囚犯的两难处境 The Prisoners’ Dilemma 优势策略是指，无论另外的参与者 采用什么策略，它都是某一参与者 所遵循的最好策略。 The dominant strategy is the best strategy for a player to follow regardless of the strategies pursued by other players. 优势策略均衡是纳什均衡的特例。 27 囚犯的两难处境 The Prisoners’ Dilemma 合作之所以难以维持，是因为 合作不是单个人的最好利益。 Cooperation is difficult to maintain, because cooperation is not in the best interest of the individual player. 28 囚徒困境式的寡头博弈 Oligopolies as a Prisoners’ Dilemma 伊拉克的决策Iraq’s Decision 高产量High Production低产量Low Production 高产量 High Production 低产量 Low Production 伊郎的决策 Iran’s Decision Iran gets $40 billion 伊朗得40亿美元 Iraq gets $40 billion 伊拉克得40亿 美元 Iraq gets $30 billion 伊拉克得30亿 美元 Iraq gets $50 billion 伊拉克得50亿 美元 Iraq gets $60 billion 伊拉克得60亿 美元 Iran gets $30 billion 伊朗得30亿美元 Iran gets $50 billion 伊朗得50亿美元 Iran gets $60 billion 伊朗得60亿美元 29 囚徒困境式的寡头博弈 Oligopolies as a Prisoners’ Dilemma 自利使得寡头很难维持合作的结果，即 低产量、高价格和垄断利润。 Self-interest makes it difficult for the oligopoly to maintain a cooperative outcome with low production, high prices, and monopoly profits. 30 军备竞赛博弈 An Arms-Race Game 美国的决策 Decision of the United States (U.S.) 军备Arm裁军Disarm 军备Arm 裁军Disarm 苏联的决策 Decision of the Soviet Union (USSR) 苏联危险 USSR at risk 美国危险 U.S. at risk 美国危险并软弱 U.S. at risk and weak 美国安全 U.S. safe 美国安全并强大 U.S. safe and powerful 苏联危险并软弱 USSR at risk and weak 苏联安全 USSR safe 苏联安全并强大 USSR safe and powerful 6 31 做广告博弈 An Advertising Game 万宝路的决策Marlboro’s Decision 做广告Advertise不做广告Don’t Advertise 做广告 Advertise 不做广告 Don’t Advertise 骆驼的决策 Camel’s Decision Camel gets $3 billion profit 骆驼得30亿利润 Marlboro gets $3 billion profit 万宝路得30亿 利润 Marlboro gets $2 billion profit 万宝路得20亿 利润 Marlboro gets $4 billion profit 万宝路得40亿 利润 Marlboro gets $5 billion profit 万宝路得50亿 利润 Camel gets $2 billion profit 骆驼得20亿利润 Camel gets $4 billion profit 骆驼得40亿利润 Camel gets $5 billion profit 骆驼得50亿利润 32 共有资源博弈 A Common-Resources Game 埃克森的决策Exxon’s Decision 打两口井Drill Two Wells打一口井Drill One Well 打两口井 Drill Two Wells 打一口井 Drill One Well 阿尔科的 决策 Arco’s Decision Arco gets $4 million profit 阿尔科得4百万 Exxon gets $4 million profit 埃克森得 4百万 Exxon gets $3 million profit 埃克森得 3百万 Exxon gets $5 million profit 埃克森得 5百万 Exxon gets $6 million profit 埃克森得 6百万 Arco gets $3 million profit 阿尔科得3百万 Arco gets $5 million profit 阿尔科得5百万 Arco gets $6 million profit 阿尔科得6百万 33 杰克和吉尔的寡头博弈 Jack and Jill’s Oligopoly Game 杰克的决策Jack’s Decision 出售40加仑 Sell 40 gallons 出售30加仑 Sell 30 gallons 出售40加仑 Sell 40 gallons 出售30加仑 Sell 30 gallons 吉尔的决策 Jill’s Decision Jill gets $1,600 profit 吉尔利润1600美元 Jack gets $1,600 profit 杰克利润 1600美元 Jack gets $1,500 profit 杰克利润 1500美元 Jack gets $1,800 profit 杰克利润 1800美元 Jack gets $2,000 profit 杰克利润 2000美元 Jill gets $1,500 profit 吉尔利润1500美元 Jill gets $1,800 profit 吉尔利润1800美元 Jill gets $2,000 profit 吉尔利润2000美元 34 为什么人们有时能合作 Why People Sometimes Cooperate 当企业都非常在乎未来利润时，它们会 在重复博弈中合作，而不为了获得一次 性的好处而在一次博弈中欺骗。 Firms that care about future profits will cooperate in repeated games rather than cheating in a single game to achieve a one-time gain. 35 针对寡头的公共政策 Public Policy Toward Oligopolies 从整个社会的角度看，寡头之间的合作是 不合意的，因为它使产量太低价格太高。 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. 36 贸易限制与反托拉斯法 Restraint of Trade and the Antitrust Laws ?反托拉斯法把限制贸易或企图垄断市场定为非 法。 Antitrust laws make it illegal to restrain trade or attempt to monopolize a market. ?谢尔曼反托拉斯法（1890） Sherman Antitrust Act of 1890 ?克莱顿法（1914） Clayton Act of 1914 7 37 关于反托拉斯政策的争议 Controversies over Antitrust Policy ?反托拉斯政策有时可能不允许有潜在正面 效果的商业行为。 Antitrust policies sometimes may not allow business practices that have potentially positive effects: ?转售价格控制Resale price maintenance ?掠夺性定价Predatory pricing ?搭售Tying 38 转售价格控制 Resale Price Maintenance 转售价格控制（或称公平贸易）：供应商 （比如批发商）要求零售商向顾客收取指 定的价格。 Resale price maintenance (or fair trade) occurs when suppliers (like wholesalers) require the retailers that they sell to, to charge customers a specific amount. 39 掠夺性定价 Predatory Pricing 掠夺性定价：大企业减价的动机是把它 的竞争对手赶出市场。 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. 40 搭售 Tying 搭售：一个企业以单一价格提供两 个或多个产品，而不是分开提供。 Tying refers to when a firm offers two (or more) of its products together at a single price, rather than separately. 41 总结 Summary ?寡头通过组成卡特尔，象一个垄断者那样行事 ，以最大化他们的总利润。 Oligopolists maximize their total profits by forming a cartel and acting like a monopolist. ?如果寡头单独地进行产量决策，结果是比垄断 更高的数量和更低的价格。 If oligopolists make decisions about production levels individually, the result is a greater quantity and a lower price than under the monopoly outcome. 42 总结 Summary ?囚徒困境表明，自利的行为阻止人们进行合作 ，即使合作符合双方各自的利益。 The prisoners’ dilemma shows that self-interest can prevent people from maintaining cooperation, even when cooperation is in their mutual self-interest. ?囚徒困境的逻辑可以应用于许多场合，包括寡 头。 The logic of the prisoners’ dilemma applies in many situations, including oligopolies. 8 43 总结 Summary ?政策制定者运用反托拉斯法来阻止寡头 做出妨碍竞争的举动。 Policymakers use the antitrust laws to prevent oligopolies from engaging in behavior that reduces competition.