曼昆经济学Chap_17

利润
需求
MR
0
利润最大化产量
产量
Monopolistic Competition in the Short Run
Short-run economic losses encourage firms to exit the market. This:
u
u
u
u
Decreases the number of products offered. Increases demand faced by the remaining firms. Shifts the remaining firms’ demand curves to the right. Increases the remaining firms’ profits.
(a) Firm Makes Profit Price MC ATC
Price Average total cost Profit MR 0 Profitmaximizing quantity Quantity
Demand
图1. 短期中的垄断竞争企业
(a) 企业有利润
价格
MC
ATC
价格 平均 总成本
餐馆、钢琴课、点心、家居等等。
Product Differentiation
Each firm produces a product that is at least slightly different from those of other firms. Rather than being a price taker, each firm faces a downwardsloping demand curve.
需求 产量
Long-Run Equilibrium
Two Characteristics
As in a monopoly, price exceeds marginal cost.
Profit maximization requires marginal revenue to equal marginal cost. The downward-sloping demand curve makes marginal revenue less than price.
Figure 2 A Monopolistic Competitor in the Long Run
Price MC
ATC
P = ATC
Demand MR 0 Profit-maximizing quantity Quantity
图2. 长期中的垄断竞争者
价格
MC ATC
P=ATC
MR
0 利润最大化产量
垄断竞争与完全竞争
过剩生产能力
在长期中，完全竞争企业没有过剩生产能力。 竞争市场上的自由进出使企业生产平均总成本 最小的产量，即企业的有效规模产量。 在长期中，垄断竞争企业存在过剩生产能力。 垄断竞争企业的产量低于完全竞争企业生产的 有效规模产量。
Figure 3 Monopolistic versus Perfect Competition
u u
u
u
Increases the number of products offered. Reduces demand faced by firms already in the market. Incumbent firms’ demand curves shift to the left. Demand for the incumbent firms’ products fall, and their profits decline.
自由进入或退出
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u
企业可以没有限制地进入或退出一 个市场。 市场上企业的数量要一直调整到经 济利润为零时为止。
12.3 Monopolistic Competition in the Short Run
Short-run economic profits encourage new firms to enter the market. This:
u
u
产品差异化
u
每个企业生产的一种产品至少与其他 企业生产的这种产品略有不同。 每个企业不是价格接受者，而是面临 一条向右下方倾斜的需求曲线。
u
Free Entry or Exit
u
u
Firms can enter or exit the market without restriction. The number of firms in the market adjusts until economic profits are zero.
Quantity
0
Quantity produced = Efficient scale
Quantity
图3. 垄断竞争与完全竞争
(a) 垄断竞争企业
价格 价格
(b) 完全竞争企业 MC MC
ATC
ATC
P 过剩生产能力 需求 产量 生产量 有效规模
P = MC P = MR (需求曲线)
产量 产量 = 有效规模产量
(a) Monopolistically Competitive Firm Price MC
Markup
(b) Perfectly Competitive Firm Price MC
ATC
ATC
P
P = MC
Marginal cost MR Demand
P = MR (demand curve)
0
Quantity produced
Quantity
0
Quantity produced
Quantity
图3. 高于边际成本的价格加成
(a) 垄断竞争企业
价格 价格加成 价格
(b) 完全竞争企业
MC
ATC
MC
ATC
P = MC
边际成本
P = MR
(需求曲线)
MR
需求 产量 产量 生产量
生产量
(b) Firm Makes Losses Price MC Losses ATC
Average total cost Price
MR
0 Lossminimizing quantity
Demand Quantity
图1. 短期中的垄断竞争企业
(b) 企业亏损
价格 亏损 平均 总成本 价格 需求
MC
垄断竞争与完全竞争
高于边际成本的价格加成
对一个竞争企业来说，价格等于边际成 本。 对一个垄断竞争企业来说，价格高于边 际成本。 因为垄断竞争企业的价格高于其边际成 本，以现价多销售出一个单位产品就意 味着利润多了。
Figure 3 Monopolistic versus Perfect Competition
uProduct
examples include books, CDs, movies, computer games, restaurants, piano lessons, cookies, furniture, etc.
很多卖者
有许多企业争夺同样的顾客群体。
u产品例子包括书籍、CD、电影、电脑游戏、
Monopolistic Competition
垄断竞争
Chapter 17
Monopolistic Competition 垄断竞争
Markets that have some features of competition and some features of monopoly. 有某些竞争特点又有某些垄断特点的 市场结构。
ATC
MR
0
利润最小化产量
产量
12.4 The Long-Run Equilibrium 长期均衡
Firms will enter and exit until the firms are making exactly zero economic profits. 企业进入或退出的过程一直持续到市 场中的企业的经济利润正好是零时。
As in a competitive market, price equals average total cost.
Free entry and exit drive economic profit to zero.
长期均衡
两个特点
正如在垄断市场上一样，价格大于边际成本。
利润最大化要求边际收益等于边际成本。 向右下方倾斜的需求曲线使边际成本小于价格。
Monopolistic versus Perfect Competition
Markup Over Marginal Cost
For a competitive firm, price equals marginal cost. For a monopolistically competitive firm, price exceeds marginal cost. Because price exceeds marginal cost, an extra unit sold at the posted price means more profit for the monopolistically competitive firm.
短期中的垄断竞争企业
短期 经济利润激励新企业进入市场。这种 进入
u
u
增加了顾客可以选择的产品数量。
减少了市场已有的每家企业面临的需求。
u
u
使市场已有企业面临的需求曲线向左移动。
市场已有企业的产品需求减少，利润下降。
Figure 1 Monopolistic Competition in the Short Run
(a) Monopolistically Competitive Firm Price MC Price
(b) Perfectly Competitive Firm
ATC
MC
ATC
P
P = MC
P = MR (demand curve)
MR
Demand
0
Quantity produced
Efficient scale
垄断竞争与完全竞争
垄断竞争和完全竞争之间有两个值 得注意的差别—过剩生产能力 和 价格加成。
Monopolistic versus Perfect Competition
Excess Capacity
There is no excess capacity in perfect competition in the long run. Free entry results in competitive firms producing at the point where average total cost is minimized, which is the efficient scale of the firm. There is excess capacity in monopolistic competition in the long run. In monopolistic competition, output is less than the efficient scale of perfect competition.
12.2 Attributes of Monopolistic competition 垄断竞争的特点
u
Hale Waihona Puke uuMany sellers 很多卖者 Product differentiation 产品有差异 Free entry and exit 自由进入和退出
Many Sellers
There are many firms competing for the same group of customers.
短期中的垄断竞争企业
短期经济亏损激励企业退出市场。随着 企业退出：
u u u
u
顾客可选择的产品数量少了。 增加了继续留在市场中的企业面临的需求。 使继续留在市场中的企业的需求曲线向右移 动。 使继续留在市场中的企业的利润增加。
Figure 1 Monopolistic Competitors in the Short Run
正如在竞争市场上一样，价格等于平均总成 本。
自由进入与退出使经济利润为零。
12.5 Monopolistic versus Perfect Competition
There are two noteworthy differences between monopolistic and perfect competition—excess capacity and markup.