寡头垄断市场上的价格和产量的决定
7.5 Decision of Price and Output
Under Oligopoly Market
教学目标 Objectives：
? 了解寡头垄断的市场特征
? 掌握寡头垄断市场勾结情况下价格和产量的决定
? 掌握寡头垄断市场不勾结情况下价格和产量的决定
? 掌握四种市场结构的比较
知识点 Knowledge：
价格领先制, 卡特尔, 四种市场结构的比较
技能点 Skills：
理解寡头垄断市场上价格和产量的决定
Oligopoly Market
price-taker
interdependence
market structure
tacit collusion
intensive marketing campaign
cartel
quota
Barometric price leadership
Dominant firm price leadership
Price Benchmarks
THE KINKED DEMAND CURVE
专业词汇 Professional terms
1 DEFINITION AND FEATURES OF OLIGOPOLY
Oligopoly describes a market structure where just a
few firms between them control a large proportion
of the industry,It is probably the most dominant
market structure in the UK today,Most
oligopolists produce differentiated products and
much of the competition between them is in the
marketing of their particular brands,The greater
the product differentiation,the greater the scope to
be a price-maker rather than a price-taker.
1 DEFINITION AND FEATURES OF OLIGOPOLY
Despite the differences between firms in
oligopolistic markets,there are therefore two key
features that distinguish oligopoly from other
market structures:
1,Barriers to entry,The size of the barrier will
differ from industry to industry,In some cases
entry is relatively easy,while in others it is very
difficult.
2,Interdependence of the firms.
1 DEFINITION AND FEATURES OF OLIGOPOLY
寡头市场在价格与产量决策上有以下三方面特点：
?一是它很难对产量与价格问题做出像前三种市场类型
那样确切而肯定的答案 。
?二是价格和产量一旦确定以后, 就有其相对稳定性 。
这也就是说, 各个寡头由于难以捉摸对手的行为, 一
般不会轻易变动已确定的价格与产量水平 。
?三是各寡头之间的相互依存性, 使他们之间更容易形
成某种形式的勾结 。 但各寡头之间的利益又是矛盾的,
这就决定了勾结不能代替或取消竞争, 寡头之间的竞
争往往会更加激烈 。 这种竞争有价格竞争, 也有非价
格竞争 。
2 COMPETITION AND COLLUSION
Oligopolists are pulled in two different
directions:
1,The mutually dependence of firms may tempt
them to join together,If they collude in this
manner they could jointly maximize industry
profits.
2,On the other hand there is a great temptation
for an individual firm to compete with its rivals to
gain market share.
2,1 COLLUSIVE OLIGOPOLY
Collusive oligopoly occurs where firms agree,
either formally or informally,to limit the
competition between them,They may agree on
prices,market share,advertising expenditure etc.
Such collusion will reduce the uncertainty the firms
face in a fiercely competitive environment,It will
reduce the fear of engaging in competitive price-
cutting or other strategies,which could reduce total
industry profit.
2,1 COLLUSIVE OLIGOPOLY
P
Profit-maximising cartel
The total market demand
curve is shown with the
corresponding market
MR curve,The cartel’s
MC curve is the
horizontal sum of the MC
curves of its members.
This is because we are
adding the output of each
of the cartel members at
each level of marginal
cost,Profits are
maximized at Q where
MC=MR,The cartel will
therefore set a price of P
at which Q will be
demanded.
Q Quantity0
Industry
MR
Industry
D=AR
Industry
MC
Price
Figure 1,Profit-maximizing
cartel
2.2 HOW DOES THE CARTEL DIVIDE UP THE
MARKET?
one way of dividing the market would be by
using non-price competition for each firm to
gain as big a share of the resulting sales as
they can.
Another method would be for each of the
cartel members to agree on dividing the
market up between them in a particular way
so that each member is given a quota.
2,3 TACIT COLLUSION
--1,Dominant Firm Price Leadership
D leader
P
P1
Figure 2(a) shows the total
demand curve,The supply curve
for all the followers is also shown,
These firms accept the price set by
the leader and their joint supply
curve is simply the sum of their
MC curves.
The leader’s demand curve can be
seen as that portion of market
demand unfilled by the other
firms,At P the whole of market
demand is satisfied by the other
firms,and so the demand for the
leader is zero (point a),At P1 the
other firms’ supply is zero,and so
the leader faces the full market
demand (point b),The leader’s
demand curve thus connects points
a and b.(Division of market between leader and followers
0 Quantity
Price
S all other firms
D market
2,3 TACIT COLLUSION
--1,Dominant Firm Price Leadership
0 QL QF QT
Quantity
MC leaderD market
Dleader
The leader’s profit will be
maximised where its marginal
cost equals its marginal revenue.
This is shown in Figure 2 (b)
opposite,The leader’s marginal
cost equals its marginal revenue
at an output of QL,giving a point
l on its demand curve,The
leader then sets a price of PL,
which the others then follow.
They supply QF,at a point f on
their supply curve,Total market
demand at PL is QT,which is
point t on the market demand
curve,Total output QT must add
up to the output of both leaders
and followers,QL and QF.
MC leader
S all otherfirms
Price
PL
(b) Determination of price and output
2,3 TACIT COLLUSION
2.Barometric Firm Price Leadership
A similar model could be constructed for a barometric firm.
Although the firm is not dominating the industry,the others
will follow its price,In practice,which firm is taken as the
barometer will frequently change,Whether we are talking
about food retailers,oil companies,car producers or banks,
any firm may take the initiative in raising prices,If the
other firms are merely waiting for someone to take the lead,
say because costs have risen,they will quickly follow suit.
3,NON-COLLUSIVE OLIGOPOLY
MC
The figure opposite assumes a
cartel consisting of five equal-
sized firms,The cartel sets the
industry profit-maximising price
of ￡10,This will give an industry
output of 1000 units,The cartel
divides this output equally
between its five members,i.e,each
member has a quota of 200 units.
12
10
8
6
4
2
0
1000 2000 3000
Quantity
MR
AR
Price
(a) The industry
3,NON-COLLUSIVE OLIGOPOLY
MC
C Cart
Cartel price
(=MR if
price
remains
fixed
Price
Diagram 3 (b) opposite shows the
position for one of the members of
the cartel,Firm A,If the cartel’s
price remains fixed at ￡10,then
￡10 is also the MR for the
individual firm,Firm A would
maximise its own profits by selling
600 units,where MC=P=MR,
provided it could do this by taking
market share off the other
members,This would leave total
industry output,and hence price,
unaffected.
Alternatively,Firm A could
maximise profits by cutting price
to ￡8 and thereby increasing its
sales to 400 units.
200 400 600
800
12
10
8
6
4
2
0
MR AR
(b) Firm A
3,NON-COLLUSIVE OLIGOPOLY
A ￡10m each B ￡5m each
￡12m each
C ￡12m for Y D ￡8m each
￡5 for X
￡2
￡1.80
￡2 ￡1.80
Y’s price
X’s price
3,NON-COLLUSIVE OLIGOPOLY
STABLE CONDITIONS UNDER A
KINKED DEMAND CURVE
If a demand curve is drawn made on the
assumptions made above,it will be
kinked at the present price and output.
This is because demand is relatively
elastic above the price,and relatively
inelastic below the price.
The upper part of the demand curve is
elastic,as a rise in price will lead to a
large fall in sales as consumers switch to
the now relatively lower-priced rivals.
The lower part of the demand curve is
inelastic,as a fall in price will only bring
in modest increases in sales,since rivals
also lower their prices.
The firm will thus be reluctant to lower
its price or to raise its price,Thus
oligopolists will be reluctant to change
prices at all.
0 Q1 Quantity
P1
Price (￡)
D
3,NON-COLLUSIVE OLIGOPOLY
This price stability can be shown in the
diagram opposite,At quantities less
than Q1 the MR curve will correspond
to the shallow part of the AR curve,At
quantities greater than Q1 the MR
curve will correspond to the steep part
of the AR curve (the dotted lines
drawn backwards to the vertical axis).
When these two lines are combined to
form the MR curve,it can seen that
there is a gap between points a and b.
In other words there is a vertical
section of the Mr curve between these
two points.
Profits are maximised when MR=MC.
Thus,if the MC curve lies anywhere
between MC1 and MC2,the profit-
maximising price and output will
remain at P1 and Q2,despite a
considerable change in Price.
Price (￡)
P1
0 Q1 MR Quantity
D =AR
MC1
MC2
a
b
4,EVALUATION OF OLIGOPOLY
很明显, 寡头垄断往往会抬高价格, 损害
消费者利益和社会经济福利 。 但寡头垄断
有利于实现规模经济和促进科学技术进步,
对经济的发展是有推动作用的 。
5,COMPARATION BETWEEN THE FOUR
KINDS OF MARKET
四种市场结构的厂商均衡状态的比较
市场类
型
厂商
数量
及其
规模
对价格
的影响
均衡条件
（ MR=MC） 评
价
短期均衡 长期均衡
完
全
竞
争
很多小
厂商 。
产品
同质
由市场决定,
个别厂商无
法决定
P=MR=AR
MR=MC
超额利润＝ (AR－ AC) q
（ 可以＞ 0,＝ 0或＜ 0）
MR=AR=MC=AC。
只是正常利润 。
因 AR = MC,成本最小化
,从而经济效率最高 。
供求平衡, 成
本低, 价格低
完
全
垄
断
一家
有很高的控
制力
AR＞ MR
MR=MC（ SMC）
超额利润
＝ (AR－ AC) q（ 可＞ 0,＝
0或＜ 0）
MR=LMC=SMC
有超额利润 （ 但公营的公用
事业可能没有 ）
成本与价格高，
产量低
垄
断
竞
争
较多
产品差
别性
由市场决定,
但个别厂商
略有影响
MR=MC
超额利润
＝ (AR－ AC) q（ 可＞ 0,＝
0或＜ 0）
MR=MC,P（ AR） =AC
只能获得正常利润
AC ＞ MC,P（ AR ） ＞
MR。
介于完全竞争
与完全垄断之
间
寡
头
垄
断
少数
几家
有控制能力
按利润最大化原则通过卡特尔, 价格领先制, 成本加成法等形
式决定 。
短期超额利润＝ (AR－ AC) q（ 同样可＞ 0,＝ 0或＜ 0） 。 长期
通常有超额利润 。
抬高价格，但
有利于规模扩
大和科技创新
7.5 Decision of Price and Output
Under Oligopoly Market
教学目标 Objectives：
? 了解寡头垄断的市场特征
? 掌握寡头垄断市场勾结情况下价格和产量的决定
? 掌握寡头垄断市场不勾结情况下价格和产量的决定
? 掌握四种市场结构的比较
知识点 Knowledge：
价格领先制, 卡特尔, 四种市场结构的比较
技能点 Skills：
理解寡头垄断市场上价格和产量的决定
Oligopoly Market
price-taker
interdependence
market structure
tacit collusion
intensive marketing campaign
cartel
quota
Barometric price leadership
Dominant firm price leadership
Price Benchmarks
THE KINKED DEMAND CURVE
专业词汇 Professional terms
1 DEFINITION AND FEATURES OF OLIGOPOLY
Oligopoly describes a market structure where just a
few firms between them control a large proportion
of the industry,It is probably the most dominant
market structure in the UK today,Most
oligopolists produce differentiated products and
much of the competition between them is in the
marketing of their particular brands,The greater
the product differentiation,the greater the scope to
be a price-maker rather than a price-taker.
1 DEFINITION AND FEATURES OF OLIGOPOLY
Despite the differences between firms in
oligopolistic markets,there are therefore two key
features that distinguish oligopoly from other
market structures:
1,Barriers to entry,The size of the barrier will
differ from industry to industry,In some cases
entry is relatively easy,while in others it is very
difficult.
2,Interdependence of the firms.
1 DEFINITION AND FEATURES OF OLIGOPOLY
寡头市场在价格与产量决策上有以下三方面特点：
?一是它很难对产量与价格问题做出像前三种市场类型
那样确切而肯定的答案 。
?二是价格和产量一旦确定以后, 就有其相对稳定性 。
这也就是说, 各个寡头由于难以捉摸对手的行为, 一
般不会轻易变动已确定的价格与产量水平 。
?三是各寡头之间的相互依存性, 使他们之间更容易形
成某种形式的勾结 。 但各寡头之间的利益又是矛盾的,
这就决定了勾结不能代替或取消竞争, 寡头之间的竞
争往往会更加激烈 。 这种竞争有价格竞争, 也有非价
格竞争 。
2 COMPETITION AND COLLUSION
Oligopolists are pulled in two different
directions:
1,The mutually dependence of firms may tempt
them to join together,If they collude in this
manner they could jointly maximize industry
profits.
2,On the other hand there is a great temptation
for an individual firm to compete with its rivals to
gain market share.
2,1 COLLUSIVE OLIGOPOLY
Collusive oligopoly occurs where firms agree,
either formally or informally,to limit the
competition between them,They may agree on
prices,market share,advertising expenditure etc.
Such collusion will reduce the uncertainty the firms
face in a fiercely competitive environment,It will
reduce the fear of engaging in competitive price-
cutting or other strategies,which could reduce total
industry profit.
2,1 COLLUSIVE OLIGOPOLY
P
Profit-maximising cartel
The total market demand
curve is shown with the
corresponding market
MR curve,The cartel’s
MC curve is the
horizontal sum of the MC
curves of its members.
This is because we are
adding the output of each
of the cartel members at
each level of marginal
cost,Profits are
maximized at Q where
MC=MR,The cartel will
therefore set a price of P
at which Q will be
demanded.
Q Quantity0
Industry
MR
Industry
D=AR
Industry
MC
Price
Figure 1,Profit-maximizing
cartel
2.2 HOW DOES THE CARTEL DIVIDE UP THE
MARKET?
one way of dividing the market would be by
using non-price competition for each firm to
gain as big a share of the resulting sales as
they can.
Another method would be for each of the
cartel members to agree on dividing the
market up between them in a particular way
so that each member is given a quota.
2,3 TACIT COLLUSION
--1,Dominant Firm Price Leadership
D leader
P
P1
Figure 2(a) shows the total
demand curve,The supply curve
for all the followers is also shown,
These firms accept the price set by
the leader and their joint supply
curve is simply the sum of their
MC curves.
The leader’s demand curve can be
seen as that portion of market
demand unfilled by the other
firms,At P the whole of market
demand is satisfied by the other
firms,and so the demand for the
leader is zero (point a),At P1 the
other firms’ supply is zero,and so
the leader faces the full market
demand (point b),The leader’s
demand curve thus connects points
a and b.(Division of market between leader and followers
0 Quantity
Price
S all other firms
D market
2,3 TACIT COLLUSION
--1,Dominant Firm Price Leadership
0 QL QF QT
Quantity
MC leaderD market
Dleader
The leader’s profit will be
maximised where its marginal
cost equals its marginal revenue.
This is shown in Figure 2 (b)
opposite,The leader’s marginal
cost equals its marginal revenue
at an output of QL,giving a point
l on its demand curve,The
leader then sets a price of PL,
which the others then follow.
They supply QF,at a point f on
their supply curve,Total market
demand at PL is QT,which is
point t on the market demand
curve,Total output QT must add
up to the output of both leaders
and followers,QL and QF.
MC leader
S all otherfirms
Price
PL
(b) Determination of price and output
2,3 TACIT COLLUSION
2.Barometric Firm Price Leadership
A similar model could be constructed for a barometric firm.
Although the firm is not dominating the industry,the others
will follow its price,In practice,which firm is taken as the
barometer will frequently change,Whether we are talking
about food retailers,oil companies,car producers or banks,
any firm may take the initiative in raising prices,If the
other firms are merely waiting for someone to take the lead,
say because costs have risen,they will quickly follow suit.
3,NON-COLLUSIVE OLIGOPOLY
MC
The figure opposite assumes a
cartel consisting of five equal-
sized firms,The cartel sets the
industry profit-maximising price
of ￡10,This will give an industry
output of 1000 units,The cartel
divides this output equally
between its five members,i.e,each
member has a quota of 200 units.
12
10
8
6
4
2
0
1000 2000 3000
Quantity
MR
AR
Price
(a) The industry
3,NON-COLLUSIVE OLIGOPOLY
MC
C Cart
Cartel price
(=MR if
price
remains
fixed
Price
Diagram 3 (b) opposite shows the
position for one of the members of
the cartel,Firm A,If the cartel’s
price remains fixed at ￡10,then
￡10 is also the MR for the
individual firm,Firm A would
maximise its own profits by selling
600 units,where MC=P=MR,
provided it could do this by taking
market share off the other
members,This would leave total
industry output,and hence price,
unaffected.
Alternatively,Firm A could
maximise profits by cutting price
to ￡8 and thereby increasing its
sales to 400 units.
200 400 600
800
12
10
8
6
4
2
0
MR AR
(b) Firm A
3,NON-COLLUSIVE OLIGOPOLY
A ￡10m each B ￡5m each
￡12m each
C ￡12m for Y D ￡8m each
￡5 for X
￡2
￡1.80
￡2 ￡1.80
Y’s price
X’s price
3,NON-COLLUSIVE OLIGOPOLY
STABLE CONDITIONS UNDER A
KINKED DEMAND CURVE
If a demand curve is drawn made on the
assumptions made above,it will be
kinked at the present price and output.
This is because demand is relatively
elastic above the price,and relatively
inelastic below the price.
The upper part of the demand curve is
elastic,as a rise in price will lead to a
large fall in sales as consumers switch to
the now relatively lower-priced rivals.
The lower part of the demand curve is
inelastic,as a fall in price will only bring
in modest increases in sales,since rivals
also lower their prices.
The firm will thus be reluctant to lower
its price or to raise its price,Thus
oligopolists will be reluctant to change
prices at all.
0 Q1 Quantity
P1
Price (￡)
D
3,NON-COLLUSIVE OLIGOPOLY
This price stability can be shown in the
diagram opposite,At quantities less
than Q1 the MR curve will correspond
to the shallow part of the AR curve,At
quantities greater than Q1 the MR
curve will correspond to the steep part
of the AR curve (the dotted lines
drawn backwards to the vertical axis).
When these two lines are combined to
form the MR curve,it can seen that
there is a gap between points a and b.
In other words there is a vertical
section of the Mr curve between these
two points.
Profits are maximised when MR=MC.
Thus,if the MC curve lies anywhere
between MC1 and MC2,the profit-
maximising price and output will
remain at P1 and Q2,despite a
considerable change in Price.
Price (￡)
P1
0 Q1 MR Quantity
D =AR
MC1
MC2
a
b
4,EVALUATION OF OLIGOPOLY
很明显, 寡头垄断往往会抬高价格, 损害
消费者利益和社会经济福利 。 但寡头垄断
有利于实现规模经济和促进科学技术进步,
对经济的发展是有推动作用的 。
5,COMPARATION BETWEEN THE FOUR
KINDS OF MARKET
四种市场结构的厂商均衡状态的比较
市场类
型
厂商
数量
及其
规模
对价格
的影响
均衡条件
（ MR=MC） 评
价
短期均衡 长期均衡
完
全
竞
争
很多小
厂商 。
产品
同质
由市场决定,
个别厂商无
法决定
P=MR=AR
MR=MC
超额利润＝ (AR－ AC) q
（ 可以＞ 0,＝ 0或＜ 0）
MR=AR=MC=AC。
只是正常利润 。
因 AR = MC,成本最小化
,从而经济效率最高 。
供求平衡, 成
本低, 价格低
完
全
垄
断
一家
有很高的控
制力
AR＞ MR
MR=MC（ SMC）
超额利润
＝ (AR－ AC) q（ 可＞ 0,＝
0或＜ 0）
MR=LMC=SMC
有超额利润 （ 但公营的公用
事业可能没有 ）
成本与价格高，
产量低
垄
断
竞
争
较多
产品差
别性
由市场决定,
但个别厂商
略有影响
MR=MC
超额利润
＝ (AR－ AC) q（ 可＞ 0,＝
0或＜ 0）
MR=MC,P（ AR） =AC
只能获得正常利润
AC ＞ MC,P（ AR ） ＞
MR。
介于完全竞争
与完全垄断之
间
寡
头
垄
断
少数
几家
有控制能力
按利润最大化原则通过卡特尔, 价格领先制, 成本加成法等形
式决定 。
短期超额利润＝ (AR－ AC) q（ 同样可＞ 0,＝ 0或＜ 0） 。 长期
通常有超额利润 。
抬高价格，但
有利于规模扩
大和科技创新
