1
竞争市场上的企业
Firms in Competitive
Markets
第14章
Chapter 14
2
竞争的含义
The Meaning of Competition
?完全竞争市场具有下列特征:
A perfectly competitive market has the
following characteristics:
?市场中有许多买者和卖者
There are many buyers and sellers in the
market.
?各个卖者提供的物品大体上是相同的
The goods offered by the various sellers are
largely the same.
?企业可以自由地进入或退出市场
Firms can freely enter or exit the market.
3
竞争的含义
The Meaning of Competition
?这些特征，使得完全竞争市场具有如下结果：
As a result of its characteristics, the perfectly
competitive market has the following outcomes:
?任何一个买者或卖者的行动对市场价格的影响都
可以忽略不计。
The actions of any single buyer or seller in the
market have a negligible impact on the market
price.
?每一个买者和卖者都接受市场决定的价格。
Each buyer and seller takes the market price as
given.
4
竞争的含义
The Meaning of Competition
竞争市场中的买者和卖者被称为价格
接受者。
Buyers and sellers in competitive
markets are said to be price takers.
5
竞争企业的收益
Revenue of a Competitive Firm
企业的总收益是销售价格乘以销售量。
Total revenue for a firm is the selling
price times the quantity sold.
TR = (P X Q)
6
竞争企业的收益
Revenue of a Competitive Firm
总收益与产量成比例。
Total revenue is proportional to the
amount of output.
2
7
竞争企业的收益
Revenue of a Competitive Firm
平均收益告诉我们一个企业从每一典型单
位的销售中得到多少收益。
Average revenue tells us how much
revenue a firm receives for the typical
unit sold.
8
竞争企业的收益
Revenue of a Competitive Firm
对所有企业来说，平均收益等于物品的价格。
For all firms, average revenue equals the
price of the good.
Average revenue =
Total revenue
Quantity
=
(Price Quantity)
Quantity
=Price
×
9
竞争企业的收益
Revenue of a Competitive Firm
边际收益是销售量增加一个单位带来的总
收益的变化。
Marginal revenue is the change in total
revenue from an additional unit sold.
MR =?TR/ ?Q
10
竞争企业的收益
Revenue of a Competitive Firm
对竞争企业来说，边际收益等于物品价格。
For competitive firms, marginal revenue
equals the price of the good.
11
竞争企业的总收益、平均收益和边际收益
Total, Average, and Marginal Revenue
for a Competitive Firm
产量Quanti
ty
(Q)
价格Price
(P)
总收益Total
Revenue
(TR=PxQ)
平均收益Average
Revenue
(AR=TR/Q)
边际收益Marginal
Revenue
(MR= )
1 $6.00 $6.00 $6.00
2 $6.00 $12.00 $6.00 $6.00
3 $6.00 $18.00 $6.00 $6.00
4 $6.00 $24.00 $6.00 $6.00
5 $6.00 $30.00 $6.00 $6.00
6 $6.00 $36.00 $6.00 $6.00
7 $6.00 $42.00 $6.00 $6.00
8 $6.00 $48.00 $6.00 $6.00
QTR ?? /
12
竞争企业的利润最大化
Profit Maximization for the
Competitive Firm
?竞争企业的目标是利润最大化。
The goal of a competitive firm is to maximize
profit.
?这意味着企业将生产使总收益和总成本之差
最大的产量。
This means that the firm will want to produce
the quantity that maximizes the difference
between total revenue and total cost.
3
13
利润最大化：一个数字例子
Profit Maximization:
A Numerical Example
价格Pric
e
(P)
产量Quanti
ty
(Q)
总收益Total
Revenue
(TR=PxQ)
总成本Total
Cost
(TC)
利润Profit
(TR-TC)
边际收益Marginal
Revenue
(MR= )
边际成本Margi
nal Cost
MC=
0 $0.00 $3.00 -$3.00
$6.00 1 $6.00 $5.00 $1.00 $6.00 $2.00
$6.00 2 $12.00 $8.00 $4.00 $6.00 $3.00
$6.00 3 $18.00 $12.00 $6.00 $6.00 $4.00
$6.00 4 $24.00 $17.00 $7.00 $6.00 $5.00
$6.00 5 $30.00 $23.00 $7.00 $6.00 $6.00
$6.00 6 $36.00 $30.00 $6.00 $6.00 $7.00
$6.00 7 $42.00 $38.00 $4.00 $6.00 $8.00
$6.00 8 $48.00 $47.00 $1.00 $6.00 $9.00
QTR ?? / QTC ?? /
P = AR = MRP=MR1
MC
竞争企业的利润最大化
Profit Maximization for the Competitive Firm
产量Quantity
0
成本Costs
and
收益Revenue
ATC
AVC
Q
MAX
通过生产边际成本等于边际
收益的产量，企业使利润最
大化The firm maximizes
profit by producing the
quantity at which
marginal cost equals
marginal revenue.
MC
1
Q
1
MC
2
Q
2
15
竞争企业的利润最大化
Profit Maximization for the
Competitive Firm
在利润最大化的产量水平上，边
际收益和边际成本正好相等。
Profit maximization occurs at the
quantity where marginal revenue
equals marginal cost.
16
竞争企业的利润最大化
Profit Maximization for the
Competitive Firm
当When MR > MC 增加increase Q
当When MR < MC 减少decrease Q
当When MR = MC 利润是最大
的Profit is maximized.
17
边际成本曲线和企业的供给曲线
The Marginal-Cost Curve and the
Firm’s Supply Decision...
由于企业的边际成本曲线决定了企业
在任何一种价格时愿意供给多少，因
此，这就是竞争企业的供给曲线。
Because the firm’s marginal-cost
curve determines how much the firm
is willing to supply at any price, it is
the competitive firm’s supply curve.
边际成本曲线和企业的供给曲线
The Marginal-Cost Curve and the
Firm’s Supply Decision...
Quantity0
Costs
and
Revenue
MC
ATC
AVC
Q
1
P
1
P
2
Q
2
这部分的企业边际成本曲
线也是企业的供给曲线
This section of the
firm’s MC curve is also
the firm’s supply curve.
4
19
企业的短期停业决策
The Firm’s Short-Run Decision
to Shut Down
?停止营业指在某个特定时期，由于当前
的市场条件而不生产任何东西的短期决
策。
A shutdown refers to a short-run decision
not to produce anything during a specific
period of time because of current market
conditions.
?退出指离开市场的长期决策。
Exit refers to a long-run decision to leave
the market.
20
企业的短期停业决策
The Firm’s Short-Run Decision
to Shut Down
?当企业决定退出时，它考虑固定成本
，但当企业决定是否停业时，它不考虑
固定成本。
The firm considers its fixed costs when
deciding to exit, but ignores them when
deciding whether to shut down.
?当做出是否停业的短期决策时，固定
成本被称为沉没成本。
21
企业的短期停业决策
The Firm’s Short-Run Decision
to Shut Down
?沉没成本是那些已经发生而且无法回收
的成本。
Sunk costs are costs that have
already been committed and cannot
be recovered.
?在某种意义上说，沉没成本是机会成本
的反面：无论你做什么选择，沉没成本
不可避免。
22
企业的短期停业决策
The Firm’s Short-Run Decision
to Shut Down
?如果生产得到的收益小于生产的可变成
本时，企业就停止营业。
The firm shuts down if the revenue it gets
from producing is less than the variable
cost of production.
如果TR < VC，停业（Shut down if TR < VC）
如果TR/Q < VC/Q，停业（Shut down if TR/Q < VC/Q）
如果P < AVC，停业（Shut down if P < AVC）
23
企业的短期停业决策
The Firm’s Short-Run Decision to Shut Down
产量
Quantity
ATC
AVC
0
成本
Costs
MC
如果P < AVC，
停止营业
If P < AVC,
shut down.
如果P > AVC，
短期内继续生产
If P > AVC,
keep producing
in the short run.
如果P > ATC，
继续生产，有利润
If P > ATC,
keep producing
at a profit.
企业的短期供给曲线
Firm’s short-run
supply curve.
24
企业的短期停业决策
The Firm’s Short-Run Decision
to Shut Down
竞争企业短期供给曲线是边际成本曲线
在平均可变成本曲线以上的那一部分。
The portion of the marginal-cost curve
that lies above average variable cost is
the competitive firm’s short-run supply
curve.
5
25
企业进入或退出市场的长期决策
The Firm’s Long-Run Decision to
Exit or Enter a Market
?在长期，如果从生产中得到的收益将小于
它的总成本，企业就退出。
In the long-run, the firm exits if the revenue
it would get from producing is less than its
total cost.
如果TR < TC，退出（Exit if TR < TC）
如果TR/Q < TC/Q，退出（Exit if TR/Q < TC/Q）
如果P < ATC，退出（Exit if P < ATC）
26
企业进入或退出市场的长期决策
The Firm’s Long-Run Decision to
Exit or Enter a Market
?如果有利可图，企业就将进入这一市场。
A firm will enter the industry if such an
action would be profitable.
如果TR > TC，进入(Enter if TR > TC)
如果TR/Q > TC/Q，进入(Enter if TR/Q > TC/Q)
如果P > ATC，进入(Enter if P > ATC)
27
竞争企业的长期供给曲线
The Competitive Firm’s Long-
Run Supply Curve...
数量Quantity
MC
ATC
0
成本
Costs
如果P > ATC，企业进入
Firm enters
if P > ATC
如果P <
ATC，企业
退出
Firm exits
if P < ATC
企业的长期供给曲
线Firm’s long-
run supply curve
28
竞争企业的长期供给曲线
The Competitive Firm’s Long-
Run Supply Curve
竞争企业的长期供给曲线是边际
成本曲线位于平均总成本曲线之
上的那一部分。
The competitive firm’s long-run
supply curve is the portion of its
marginal-cost curve that lies
above average total cost.
29
企业的短期和长期供给曲线
The Firm’s Short-Run and
Long-Run Supply Curves
?短期供给曲线Short-Run Supply Curve
?边际成本曲线在平均可变成本曲线以上的那一部
分。
The portion of its marginal cost curve that lies
above average variable cost.
?长期供给曲线Long-Run Supply Curve
?边际成本曲线在平均总成本曲线最低点以上的那
一部分。
The marginal cost curve above the minimum
point of its average total cost curve.
30
利润Profit
Q
用图形来衡量竞争企业的利润
Measuring Profit in the Graph for
the Competitive Firm...
Quantity0
Price
P = AR = MR
ATCMC
P
ATC
利润最大化产量
Profit-maximizing quantity
a. 有利润的企业
A Firm with Profits
6
31
亏损
Loss
用图形来衡量竞争企业的利润
Measuring Profit in the Graph for
the Competitive Firm...
Quantity0
Price
P = AR = MR
ATCMC
P
Q
亏损最小化产量
Loss-minimizing quantity
ATC
b. 有亏损企业
A Firm with Losses
32
竞争市场中的供给
Supply in a Competitive Market
市场供给等于市场中各个企业
供给量的总和。
Market supply equals the sum
of the quantities supplied by the
individual firms in the market.
33
短期：有固定数目企业的市场
The Short Run: Market Supply
with a Fixed Number of Firms
?在任何一种既定价格上，每个企业供给
使边际成本等于价格的产量。
For any given price, each firm supplies a
quantity of output so that its marginal cost
equals price.
?市场供给曲线反应了个别企业的边际成
本曲线。
The market supply curve reflects the
individual firms’ marginal cost curves.
34
短期：有固定数目企业的市场
The Short Run: Market Supply
with a Fixed Number of Firms...
(a)个别企业供给
Individual Firm Supply
Quantity
(firm)
0
Price
(b) 市场供给
Market Supply
Quantity
(market)
Price
0
Supply
MC
1.00
$2.00
100 200
1.00
$2.00
100,000 200,000
35
长期：有进入和退出的市场供给
The Long Run: Market Supply
with Entry and Exit
?企业将进入或退出市场，直到利润被推向零。
Firms will enter or exit the market until profit is
driven to zero.
?在长期，价格等于平均总成本的最小值。
In the long run, price equals the minimum of
average total cost.
?长期市场供给曲线是一条在此价格上的水平线
The long-run market supply curve is horizontal
at this price.
36
长期：有进入和退出的市场供给
The Long Run: Market Supply
with Entry and Exit...
(a)企业的零利润条件
Firm’s Zero-Profit Condition
数量（企业）
Quantity
(firm)
0
价格
Price
P =
ATC的最小值的最小值
P =
minimum
ATC
(b) 市场供给
Market Supply
数量（市场）
Quantity
(market)
价格
Price
0
供给
Supply
MC
ATC
7
37
长期：有进入和退出的市场供给
The Long Run: Market Supply
with Entry and Exit
?当这种进入和退出过程结束是，仍然留在市场中的企
业必定得到零经济利润。
At the end of the process of entry and exit, firms that
remain must be making zero economic profit.
?只有当价格与平均总成本被推向相等时，进入与退出
过程才结束。
The process of entry & exit ends only when price and
average total cost are driven to equality.
?竞争市场长期均衡一定是企业在其有效规模点运行。
Long-run equilibrium must have firms operating at
their efficient scale.
38
为什么企业获得零利润还在经营？
Why Firms Stay in Business
with Zero Profit?
?利润等于总收益减总成本。
Profit equals total revenue minus total cost.
?总成本包括企业的所有机会成本。
Total cost includes all the opportunity costs of the firm.
?在零利润均衡时，企业的收益应该补偿所有者用于使
企业维持的时间和金钱。
In the zero-profit equilibrium, the firm’s revenue
compensates the owners for the time and money they
expend to keep the business going.
?经济利润不同于会计利润。
Economic profits differ from accounting profits.
39
需求的增加在短期内的影响
Increase in Demand in the
Short Run
?需求的增加在短期内提高价格并增加
数量。
An increase in demand raises price
and quantity in the short run.
?企业赚到正利润，因为价格现在高于
平均总成本。
Firms earn profits because price now
exceeds average total cost.
40
需求的增加在短期内和长期内的影响
Increase in Demand in the Short Run
and in the Long Run
市场Market企业Firm
Quantity
(企业firm)
0
Price
MC
ATC
P
1
Quantity
(市场market)
Price
0
D
1
P
1
Q
1
A
S
1
长期供给
Long-run
supply
(a)初始条件Initial
Condition
P
41
D
2
需求的增加在短期内和长期内的影响
Increase in Demand in the Short Run
and in the Long Run
市场MarketFirm企业
Quantity
(企业firm)
0
Price
MC ATC
P
1
Quantity
(市场market)
Price
0
D
1
P
1
Q
1
A
S
1
长期供给
Long-run
supply
(b) 短期反应Short-Run
Response
Q
2
B
P
2
P
2
利润Profit
42
需求的增加在短期内和长期内的影响
Increase in Demand in the Short Run
and in the Long Run
市场Market企业Firm
Quantity
(firm)
0
Price
MC ATC
P
1
Quantity
(market)
Price
0
D
1
P
1
Q
1
A
S
1
长期供给
Long-run
supply
(c) 长期反应Long-Run
Response
D
2
B
Q
2
P
2
S
2
C
Q
3
8
43
为什么长期供给曲线会向右上方倾斜
Why the Long-Run Supply Curve
Might Slope Upward
?一些用于生产的资源数量可能是有限
的。
Some resources used in production
may be available only in limited
quantities.
?企业可能有不同的成本。
Firms may have different costs.
44
边际企业
Marginal Firm
边际企业是如果价格有任何下
降就退出市场的企业。
The marginal firm is the firm
that would exit the market if the
price were any lower.
45
总结
Summary
?由于竞争企业是价格接受者，所以它的
收益与产量是同比例的。
Because a competitive firm is a price
taker, its revenue is proportional to the
amount of output it produces.
?物品的价格等于企业的平均收益和边际
收益。
The price of the good equals both the
firm’s average revenue and its marginal
revenue.
46
总结
Summary
?为了利润最大化，企业选择使边际收益等于边
际成本的产量。
To maximize profit a firm chooses the quantity
of output such that marginal revenue equals
marginal cost.
?这也是使价格等于边际成本的产量。
This is also the quantity at which price equals
marginal cost.
?因此，企业的边际成本曲线是它的供给曲线。
Therefore, the firm’s marginal cost curve is its
supply curve.
47
总结
Summary
?在短期中，企业不能回收其固定成本，如果物品价
格小于平均可变成本，企业将选择停止营业。
In the short run when a firm cannot recover its
fixed costs, the firm will choose to shut down
temporarily if the price of the good is less than
average variable cost.
?在长期中，企业能够回收其固定和可变成本，如果
价格小于平均总成本，企业将选择退出。
In the long run when the firm can recover both
fixed and variable costs, it will choose to exit if the
price is less than average total cost.
48
总结
Summary
?在有自由进入与退出的市场上，长期中企业利
润为零，所有企业在有效规模点生产。
In a market with free entry and exit, profits are
driven to zero in the long run and all firms
produce at the efficient scale.
?需求变动在不同时间范围之内有不同影响。
Changes in demand have different effects over
different time horizons.
