1
垄断竞争
Monopolistic
Competition
第17章
Chapter 17
2
不完全竞争市场的类型
Types of Imperfectly
Competitive Markets
?垄断竞争Monopolistic Competition
?许多企业出售类似但不相同的产品。
Many firms selling products that are similar
but not identical.
?寡头Oligopoly
?只有少数卖主，每一个提供类似的或相同的
产品。
Only a few sellers, each offering a similar or
identical product to the others.
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垄断竞争
Monopolistic Competition
市场具有某些竞争的特性也具
有某些垄断的特性。
Markets that have some
features of competition and
some features of monopoly.
4
垄断竞争的特征
Attributes of Monopolistic
Competition
?许多卖者
Many sellers
?产品差别
Product differentiation
?自由进入和退出
Free entry and exit
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许多卖者
Many Sellers
有许多企业争夺同样的顾客群体。
There are many firms competing for the same
group of customers.
?举例：书籍、CD、电影、电脑游戏、餐馆、
钢琴课、点心、家具等
Product examples include books, CDs, movies,
computer games, restaurants, piano lessons,
cookies, furniture, etc.
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产品差别
Product Differentiation
?每一个企业生产的产品至少与其他企业
生产的产品略有不同。
Each firm produces a product that is at
least slightly different from those of other
firms.
?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。
Rather than being a price taker, each
firm faces a downward-sloping demand
curve.
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7
自由进入和退出
Free Entry or Exit
?企业可以没有限制地进入和退出一个市场。
Firms can enter or exit the market without
restriction.
?市场上企业的数目要一直调整到经济利润为
零时为止。
The number of firms in the market adjusts
until economic profits are zero.
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短期中的垄断竞争企业
Monopolistic Competitors in
the Short Run...
(a) 企业有利润
Firm Makes a Profit
Quantity
0
Price
需求Demand
MR
ATC
利润Profit
MC
利润最大化产量
Profit-
maximizing quantity
价格Price
平均总成本Average
total cost
9
短期中的垄断竞争企业
Monopolistic Competitors in
the Short Run...
Quantity0
Price
需求Demand
MR
亏损Losses
(b) 企业有亏损
Firm Makes Losses
MC
ATC
平均总成本Average
total cost
亏损最小化产量
Loss- minimizing
quantity
价格Price
10
长期中的垄断竞争企业
Monopolistic Competition in
the Long Run
短期经济利润鼓励新企业进入市场。这导致：
Short-run economic profits encourage new firms to enter
the market. This:
?增加产品提供的数目。
Increases the number of products offered.
?减少已在市场中的企业面临的需求。
Reduces demand faced by firms already in the market.
?已有企业面临的需求曲线向左移动。
Incumbent firms’ demand curves shift to the left.
?随着已有企业的产品需求的减少，这些企业的利润下降。
Demand for the incumbent firms’ products fall, and their
profits decline.
11
长期中的垄断竞争企业
Monopolistic Competition in
the Long Run
短期经济亏损鼓励企业退出市场。这导致：
Short-run economic losses encourage firms to exit the
market. This:
?减少产品提供的数目。
Decreases the number of products offered.
?增加仍在市场中的企业面临的需求。
Increases demand faced by the remaining firms.
?剩余的企业面临的需求曲线向右移动。
Shifts the remaining firms’ demand curves to the right.
?增加剩余企业的利润。
Increases the remaining firms’ profits.
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长期均衡
The Long-Run Equilibrium
企业进入和退出直到市场上的
企业正好有零经济利润为止。
Firms will enter and exit until
the firms are making exactly
zero economic profits.
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长期中的垄断竞争企业
A Monopolistic Competitor
in the Long Run...
Quantity
Price
0
需求Demand
MR
ATC
MC
利润最大化产量
Profit-maximizing
quantity
P=ATC
14
长期均衡的两大特征
Two Characteristics of Long-
Run Equilibrium
?正如在垄断情况一样，价格大于边际成本。
As in a monopoly, price exceeds marginal cost.
?利润最大化要求边际收益等于边际成本。
Profit maximization requires marginal revenue to
equal marginal cost.
?向下倾斜的需求曲线使边际收益小于价格。
The downward-sloping demand curve makes
marginal revenue less than price.
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长期均衡的两大特征
Two Characteristics of Long-
Run Equilibrium
?正如在竞争市场上一样，价格等于平均总成本
As in a competitive market, price equals
average total cost.
?自由进入和退出使经济利润为零。
Free entry and exit drive economic profit to zero.
16
垄断竞争与完全竞争
Monopolistic versus Perfect
Competition
垄断竞争和完全竞争之间有两个值
得注意的差别—生产能力过剩和价
格加成。
There are two noteworthy
differences between monopolistic
and perfect competition—excess
capacity and markup.
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生产能力过剩
Excess Capacity
?在完全竞争市场中，在长期中没有生产能力
过剩。
There is no excess capacity in perfect
competition in the long run.
?自由进入使得竞争企业生产平均总成本最小
的产量，这也是企业的有效规模。
Free entry results in competitive firms
producing at the point where average total
cost is minimized, which is the efficient scale
of the firm.
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生产能力过剩
Excess Capacity
?在垄断竞争市场中，在长期中有生产
能力过剩。
There is excess capacity in
monopolistic competition in the long
run.
?在垄断竞争中，产量小于有效规模。
In monopolistic competition, output is
less than the efficient scale of perfect
competition.
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生产能力过剩...
Excess Capacity...
Quantity
(a) 垄断竞争
Monopolistically Competitive Firm
(b) 完全竞争
Perfectly Competitive Firm
Quantity
Price
P = MR
(需求曲线
demand
curve)
MC
ATC
Price
需求
Demand
MC
ATC
生产能力过剩
Excess capacity
产量
Quantity
produced
有效规模
Efficient
scale
P = MC
产量
Quantity
produced
= 有效规模
Efficient
scale
P
MR
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高于边际成本的价格加成
Markup Over Marginal Cost
?对竞争企业来说，价格等于边际成本
For a competitive firm, price equals
marginal cost.
?对垄断竞争企业来说，价格高于边际
成本。
For a monopolistically competitive
firm, price exceeds marginal cost.
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高于边际成本的价格加成
Markup Over Marginal Cost
由于价格高于边际成本，对垄断竞争
企业来说，以牌价多销售出额外的一
单位产品就意味着利润多了。
Because price exceeds marginal cost,
an extra unit sold at the posted price
means more profit for the
monopolistically competitive firm.
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高于边际成本的价格加成...
Markup Over Marginal Cost...
Quantity
(a) 垄断竞争
Monopolistically Competitive Firm
(b) 完全竞争
Perfectly Competitive Firm
Quantity
Price
P = MC P = MR
(需求曲线
demand
curve)
MC
ATC
产量
Quantity
produced
Price
P
需求Demand
边际成本
Marginal
cost
MC
ATC
MR
价格加成
Markup
产量
Quantity
produced
23
垄断竞争与完全竞争
Monopolistic versus Perfect
Competition...
Quantity
(a) Monopolistically Competitive Firm (b) Perfectly Competitive Firm
Quantity
Price
P = MR
(demand
curve)
MC
ATC
产量Quantity
produced
有效规模
Efficient
scale
Price
P
Demand
MC
ATC
P = MC
过剩生产能力
Excess capacity
边际成本
Marginal
cost
价格加成
Markup
MR
产量Quantity produced
=有效规模Efficient scale
24
垄断竞争与社会福利
Monopolistic Competition and
the Welfare of Society
垄断竞争并不具备所有完全竞争下的
合意的性质。
Monopolistic competition does not
have all the desirable properties of
perfect competition.
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25
垄断竞争与社会福利
Monopolistic Competition and
the Welfare of Society
?由于高于边际成本的价格加成，垄断竞争有垄断定价
时的标准的无谓损失。
There is the normal deadweight loss of monopoly
pricing in monopolistic competition caused by the
markup of price over marginal cost.
?但是，若管制所有生产有差别产品的企业，行政管理
负担将是巨大的。
However, the administrative burden of regulating the
pricing of all firms that produce differentiated
products would be overwhelming.
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垄断竞争与社会福利
Monopolistic Competition and
the Welfare of Society
垄断竞争可能引起社会无效率的另一个方面
是，市场上的企业数目可能并不是“理想”的
数目。可能有太多或太少的进入。
Another way in which monopolistic
competition may be socially inefficient is that
the number of firms in the market may not
be the “ideal” one. There may be too much
or too little entry.
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垄断竞争与社会福利
Monopolistic Competition and
the Welfare of Society
与进入相关的外部性包括：
Externalities of entry include:
?产品多样化的外部性。
product-variety externalities.
?抢走生意的外部性。
business-stealing externalities.
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垄断竞争与社会福利
Monopolistic Competition and
the Welfare of Society
产品多样化外部性：由于消费者从新产品
引进中得到了一些消费者剩余，所以存在
与进入相关的正外部性。
The product-variety externality: Because
consumers get some consumer surplus
from the introduction of a new product,
entry of a new firm conveys a positive
externality on consumers.
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垄断竞争与社会福利
Monopolistic Competition and
the Welfare of Society
抢走生意的外部性：由于其他企业从新竞
争者进入中失去顾客和利润，所以存在与
进入相关的负外部性。
The business-stealing externality: Because
other firms lose customers and profits from
the entry of a new competitor, entry of a
new firm imposes a negative externality on
existing firms.
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做广告
Advertising
当企业销售有差别产品，并收取高于边际
成本的价格时，每个企业都有激励以做广
告来吸引更多购买自己特殊产品的买者。
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.
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做广告
Advertising
?销售高度有差别的消费品的企业通常把收益的
10%-20%用于做广告。
Firms that sell highly differentiated consumer
goods typically spend between 10 and 20
percent of revenue on advertising.
?就美国整体经济而言，广告支出占企业总收益
的2%左右，或在1000亿美元以上。
Overall, about 2 percent of total revenue, or
over $100 billion a year, is spent on advertising.
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做广告
Advertising
?广告的批评者认为，企业做广告是为了操纵人
们的嗜好。
Critics of advertising argue that firms advertise
in order to manipulate people’s tastes.
?他们还认为，广告抑制了竞争，因为广告努力
使人们相信，产品差别大于实际情况。
They also argue that it impedes competition by
implying that products are more different than
they truly are.
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做广告
Advertising
?广告的辩护者认为，广告给消费者提供了信息。
Defenders argue that advertising provides information
to consumers
?他们还认为，广告加剧了竞争，因为它提供了产品和价
格的更多的多样性。
They also argue that advertising increases competition
by offering a greater variety of products and prices.
?企业花费广告费用的意愿可以是向消费者发出有关它的
产品的质量信号。
The willingness of a firm to spend advertising dollars
can be a signal to consumers about the quality of the
product being offered.
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品牌
Brand Names
?批评者认为，品牌使消费者感觉到的差
别大于实际存在的差别。
Critics argue that brand names cause
consumers to perceive differences that do
not really exist.
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品牌
Brand Names
?经济学家认为，品牌是消费者保证他们购买的
物品高质量的一种有用方法。
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.
?品牌向消费者提供了质量信息。
providing information about quality.
?品牌向企业提供了保持高质量的激励。
giving firms incentive to maintain high quality.
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总结
Summary
?一个垄断竞争市场有三个特征：许多企业，差
别产品和自由进入。
A monopolistically competitive market is
characterized by three attributes: many firms,
differentiated products, and free entry.
?垄断竞争市场的均衡不同于完全竞争之处在于
，每个企业有超额生产能力和收取高于边际成
本的价格。
The equilibrium in a monopolistically
competitive market differs from perfect
competition in that each firm has excess
capacity and each firm charges a price above
marginal cost.
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37
总结
Summary
?垄断竞争不同时具备完全竞争的所有合意特
性。Monopolistic competition does not have
all of the desirable properties of perfect
competition.
?由于在边际成本之上的价格加成，它有一个
标准的垄断无谓损失。
There is a standard deadweight loss of
monopoly caused by the markup of price
over marginal cost.
?企业的数目可能太多或太少。
The number of firms can be too large or too
small.
38
总结
Summary
?垄断竞争市场所固有的产品差别导致了广
告与品牌的使用。
The product differentiation inherent in
monopolistic competition leads to the use
of advertising and brand names.
?广告与品牌的批评者认为，企业使用它们是为
了利用消费者的非理性，以及减少竞争。
Critics of advertising and brand names argue
that firms use them to take advantage of
consumer irrationality and to reduce
competition.
39
总结
Summary
?辩护者认为，企业使用广告和品牌是为
了向消费者提供信息，并在价格和产品
质量上进行更激烈地竞争。
Defenders argue that firms use
advertising and brand names to inform
consumers and to compete more
vigorously on price and product quality.
