第8次课经济学竞争性垄断

1、 2007 Thomson South-WesternMonopolistic Competition 垄断竞争Imperfect competition refers to those market structures that fall between perfect competition and pure monopoly.不完全竞争是指处于完全竞争与纯粹垄断之间的那些市场结构.The Four Types of Market Structure四种市场结构的类型 Tap water Cable TVMonopoly(Chapter 15) Novels MoviesMonopoli

2、sticCompetition(Chapter 17) Tennis balls Crude oilOligopoly(Chapter 16)Number of Firms?Perfect Wheat MilkCompetition(Chapter 14)Type of Products?IdenticalproductsDifferentiatedproductsOnefirmFewfirmsManyfirmsMonopolistic Competition 垄断竞争Types of Imperfectly Competitive Markets 不完全竞争的市场类型Monopolistic

3、 Competition 垄断竞争Many firms selling products that are similar but not identical.许多企业出售类似但是并不相同的产品Oligopoly 寡头Only a few sellers, each offering a similar or identical product to the others.只有几个卖者,每一卖者提供类似的或者相同的产品。Monopolistic Competition 垄断竞争Markets that have some features of competition and some fea

4、tures of monopoly.具有竞争和垄断的某些特征的市场Attributes of monopolistic competition:垄断竞争的属性：Many sellers 有许多卖者Product differentiation 产品差异化Free entry and exit 自由进入与退出Monopolistic Competition 垄断竞争Many Sellers 有许多卖者There are many firms competing for the same group of customers.许多企业为争夺同一批顾客而竞争Product examples incl

5、ude books, CDs, movies, computer games, restaurants, piano lessons, cookies, furniture, etc.产品的范例包括书籍、CD、电影、电脑游戏、饭店、钢琴课、饼干、家具等。Monopolistic Competition 垄断竞争Product Differentiation 产品差异化Each firm produces a product that is at least slightly different from those of other firms.每一企业生产一种产品，这种产品与其他企业生产的那

6、些产品至少有略微的不同。Rather than being a price taker, each firm faces a downward-sloping demand curve.与价格的接受者不一样的是，每一企业面对的是向下倾斜的需求曲线。Monopolistic Competition 垄断竞争Free Entry or Exit 自由进入与退出Firms can enter or exit the market without restriction.企业可以没有限制地进入或退出市场The number of firms in the market adjusts until ec

7、onomic profits are zero.市场中的企业数量一直调整到利润为零时COMPETITION WITH DIFFERENTIATED PRODUCTS 差异化产品的竞争The Monopolistically Competitive Firm in the Short Run 短期中的垄断竞争企业Short-run economic profits encourage new firms to enter the market. This:短期的经济利润鼓励新的企业进入市场，这就Increases the number of products offered.增加了所提供的产品数

8、量Reduces demand faced by firms already in the market.减少了现有企业所面对的需求Incumbent firms demand curves shift to the left.企业的需求曲线向左移动Demand for the incumbent firms products fall, and their profits decline. 对于孵化期之企业的产品需求下降，并且他们的利润下降。Figure 1 Monopolistic Competition in the Short Run图1：短期中的垄断竞争Quantity0PriceP

9、rofit-maximizingquantityPriceDemandMRATC(a) Firm Makes ProfitAveragetotal costProfitMCThe Monopolistically Competitive Firm in the Short Run 短期中的垄断竞争企业Short-run economic losses encourage firms to exit the market. 短期经济亏损鼓励企业退出市场Decreases the number of products offered.减少所提供的生产数量Increases demand faced

10、 by the remaining firms.留存企业所面临的需求增加Shifts the remaining firms demand curves to the right.留存企业的需求曲线向右移动Increases the remaining firms profits.留存企业的利润增加Figure 1 Monopolistic Competitors in the Short Run图1：短期中的垄断竞争企业DemandQuantity0PricePriceLoss-minimizingquantityAveragetotal cost(b) Firm Makes LossesM

11、RLossesATCMCThe Long-Run Equilibrium 长期均衡Firms will enter and exit until the firms are making exactly zero economic profits.企业将进入和退出，直到企业获得的经济利润为零。Figure 2 A Monopolistic Competitor in the Long Run图2:长期中的垄断竞争者QuantityPrice0DemandMRATCMCProfit-maximizingquantityP = ATCThe demand curve is tangent to t

12、he ATC curve.需求曲线与ATC相切And this tangency lies vertically above the intersection of MR and MC.并且这一相切垂直于MR与MC的相交点之上The Long-Run Equilibrium 长期均衡Two Characteristics 两个特征As in a monopoly, price exceeds marginal cost.如同在垄断中那样,价格超过边际成本.Profit maximization requires marginal revenue to equal marginal cost.

13、利润最大化要求边际收益等于边际成本The downward-sloping demand curve makes marginal revenue less than price. 向下倾斜的需求曲线使得边际收益低于价格As in a competitive market, price equals average total cost.如同在竞争性市场那样，价格等于平均总成本。Free entry and exit drive economic profit to zero.自由进入与退出使经济利润趋于零Monopolistic versus Perfect Competition垄断对完全

14、竞争There are two noteworthy differences between monopolistic and perfect competition:在垄断与不完全竞争之间存在着两个值得注意的差异：Excess capacity 过剩的生产能力Markup over marginal cost 对边际成本的加成Monopolistic versus Perfect Competition垄断对完全竞争Excess Capacity 生产能力过剩There is no excess capacity in perfect competition in the long run.

15、在完全竞争中，长期内不存在生产能力过剩。Free entry results in competitive firms producing at the point where average total cost is minimized, which is the efficient scale of the firm.自由进入使得竞争性企业在平均总成本最小化的那一点上生产，该点是该企业的有效规模。There is excess capacity in monopolistic competition in the long run.在垄断竞争中，长期内存在着生产能力过剩In monopo

16、listic competition, output is less than the efficient scale of perfect competition.在垄断竞争中，产出低于不完全竞争的有效规模。Figure 3 Monopolistic versus Perfect Competition图3：垄断对不完全竞争Quantity0PriceDemand(a) Monopolistically Competitive FirmQuantity0PriceP = MCP = MR(demandcurve)(b) Perfectly Competitive FirmMCATCMCATC

17、MREfficientscalePQuantityproducedQuantity produced =Efficient scaleMonopolistic versus Perfect Competition垄断对完全竞争Markup over Marginal Cost 对边际成本的加成For a competitive firm, price equals marginal cost.对于竞争性企业来说，价格等于边际成本。For a monopolistically competitive firm, price exceeds marginal cost.对于垄断竞争企业来说，价格超

18、过边际成本。Because price exceeds marginal cost, an extra unit sold at the posted price means more profit for the monopolistically competitive firm.因为价格超过边际成本，在公布价格上多出售一个单位，就意味着垄断竞争企业获得更多的利润。Figure 3 Monopolistic versus Perfect Competition图3：垄断对完全竞争Quantity0PriceDemand(a) Monopolistically Competitive Firm

19、Quantity0PriceP = MCP = MR(demandcurve)(b) Perfectly Competitive FirmMarkupMCATCMCATCMRMarginalcostPQuantityproducedQuantity producedFigure 3 Monopolistic versus Perfect Competition图3：垄断对完全竞争Quantity0PriceDemand(a) Monopolistically Competitive FirmQuantity0PriceP = MCP = MR(demandcurve)(b) Perfectly

20、 Competitive FirmMarkupExcess capacityMCATCMCATCMRMarginalcostEfficientscalePQuantityproducedQuantity produced =Efficient scaleMonopolistic Competition and the Welfare of Society垄断竞争与社会福利Monopolistic competition does not have all the desirable properties of perfect competition.垄断竞争并不具有完全竞争所具有的所有令人欢迎

21、的属性。Monopolistic Competition and the Welfare of Society垄断竞争与社会福利There is the normal deadweight loss of monopoly pricing in monopolistic competition caused by the markup of price over marginal cost.垄断竞争中的垄断定价存在着正常的无谓损失，这是由超过边际成本的价格加成所引起的。However, the administrative burden of regulating the pricing of

22、 all firms that produce differentiated products would be overwhelming. 然而，对所有生产差异化产品的企业之定价进行规制的行政管理负担将是巨大的。Monopolistic Competition and the Welfare of Society垄断竞争与社会福利Another way in which monopolistic competition may be socially inefficient is that the number of firms in the market may not be the “i

23、deal” one. There may be too much or too little entry.另外一种方式（在此方式中垄断竞争也许对社会来说是有效的）是，市场中企业的数量也许并非“理想的”数量，也许存在着过多或者过少的进入。Monopolistic Competition and the Welfare of Society垄断竞争与社会福利Externalities of entry include: 进入的外部性包括Product-variety externalities. 生产多样性的外部性Because consumers get some consumer surplu

24、s from the introduction of a new product, entry of a new firm conveys a positive externality on consumers.因为消费者从新产品的引进中获得了某些消费者剩余， 新企业的进入产生了对消费者的正的外部性。Business-stealing externalities. 偷窃生意的外部性Because other firms lose customers and profits from the entry of a new competitor, entry of a new firm impos

25、es a negative externality on existing firms.因为其他企业由于新企业的进入而失去了顾客和利润，新企业的进入对现有企业强加了负的外部性。ADVERTISING 广告When firms sell differentiated products and charge prices above marginal cost, each firm has an incentive to advertise in order to attract more buyers to its particular product.当企业出售差异化产品并且索取超过边际成本的

26、价格时，每一企业具有做广告的激励，以便为其特定的产品吸引更多的买者。ADVERTISING 广告Firms that sell highly differentiated consumer goods typically spend between 10 and 20 percent of revenue on advertising.出售高度差异化之消费品的企业，通常把收益的10%-20%花费在做广告上。Overall, about 2 percent of total revenue, or over $200 billion a year, is spent on advertising

27、.总体上说，大约有总收入的2%，或者每年超过2000亿美圆的支出，花费在做广告上。The Debate over Advertising 有关广告的争议Critics of advertising argue that firms advertise in order to manipulate peoples tastes. 广告的批评者争论说，企业做广告是为了操纵人们的口味或偏好。They also argue that it impedes competition by implying that products are more different than they truly a

28、re.他们还争论说，通过宣扬产品的差异比它们实际存在的差异更大的隐含意思，广告妨碍了竞争。The Debate over Advertising 有关广告的争议Defenders argue that advertising provides information to consumers捍卫者争辩说，广告向消费者提供信息。They also argue that advertising increases competition by offering a greater variety of products and prices.他们还争辩说，通过提供大量的产品种类与不同价格，广告增加

29、了竞争。Advertising as a Signal of QualityThe willingness of a firm to spend advertising dollars can be a signal to consumers about the quality of the product being offered.企业花钱做广告的意愿可以成为消费者有关提供产品之质量的信号。Brand Names 商标Critics argue that brand names cause consumers to perceive differences that do not real

30、ly exist.批评者们争论说商标引起消费者认知那些并非真正存在的差异。Brand Names 商标Economists have argued that brand names may be a useful way for consumers to ensure that the goods they are buying are of high quality.经济学家争论说，商标也许是使消费者确认他们所购买的商品是高质量产品的一种有益方式。providing information about quality.提供有关质量的信息giving firms incentive to maintain high quality.向企业提供维持高质量的激励Table 1 Monopolistic Competition: Between Perfect Competition and Monopoly表1：垄断竞争-在完全竞争与垄断之间A monopolistically competitive market is characterized by three attributes: many firms, differentiated products, and free entry.垄断竞争的市场特征可以通过三个属性来认知：