微观经济学(第三版)
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微观经济学(第三版) 高鸿业. LECTURE6 完全竞争市场. 一、厂商和市场类型. 市场: 物品买卖双方相互作用并得以决定其交易价格和交易数量的一种组织形式或制度安排。 一般可将市场划分为: 完全竞争市场、垄断竞争市场、寡头市场、垄断市场 行业: 为同一商品市场生产和提供商品的所有厂商的总体。. 一、厂商和市场类型. 决定市场类型划分的主要因素有: 市场上厂商的数目; 厂商生产产品的差异程度; 单个厂商对市场价格的控制程度; 厂商进入或退出一个行业的难易程度。 其中前两因素是决定因素,后两因素是其推论和延伸。 表: PP184,6-1.

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微观经济学(第三版) 高鸿业

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4061274

微观经济学(第三版) 高鸿业

LECTURE6 完全竞争市场


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一、厂商和市场类型

  • 市场:

    • 物品买卖双方相互作用并得以决定其交易价格和交易数量的一种组织形式或制度安排。

    • 一般可将市场划分为:

      • 完全竞争市场、垄断竞争市场、寡头市场、垄断市场

  • 行业:

    • 为同一商品市场生产和提供商品的所有厂商的总体。


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一、厂商和市场类型

  • 决定市场类型划分的主要因素有:

    • 市场上厂商的数目;

    • 厂商生产产品的差异程度;

    • 单个厂商对市场价格的控制程度;

    • 厂商进入或退出一个行业的难易程度。

    • 其中前两因素是决定因素,后两因素是其推论和延伸。

    • 表:PP184,6-1


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二、完全竞争厂商的需求曲线和收益曲线

  • 完全竞争市场必须具备以下四个条件:

    • 市场上有大量的买者和卖者;

    • 每一个厂商提供的商品都是同质的;

    • 所有资源具有完全流动性;

    • 信息完全。

    • 推论:

      • 完全竞争市场是一个非个性化市场,

      • 每一个买者和卖者都是市场价格的被动接受者。


Demand and marginal revenue faced by a competitive firm

$4

d

$4

D

Demand and Marginal Revenue Facedby a Competitive Firm

Price

$ per

bushel

Price

$ per

bushel

Firm

Industry

Output

(millions

of bushels)

Output

(bushels)

100

200

100


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二、完全竞争厂商的需求曲线和收益曲线

  • 完全竞争厂商的收益曲线:

    • 完全竞争厂商平均收益曲线AR、边际收益曲线MR和需求曲线d三线重叠,都是用同一条既定市场价格水平线来表示;

    • 完全竞争厂商的总收益曲线TR则是一条由原点出发的斜率不变的上升直线。


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完全竞争厂商的收益曲线


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三、厂商实现利润最大化的均衡条件

  • 利润最大化条件:

    • 边际收益等于边际成本,MR=MC。


Marginal revenue marginal cost and profit maximization

C(q)

R(q)

A

B

q0

q*

Marginal Revenue, Marginal Cost,and Profit Maximization

  • Comparing R(q) and C(q)

    • Output levels: 0- q0:

      • C(q)> R(q)

        • Negative profit

      • FC + VC > R(q)

      • MR > MC

        • Indicates higher profit at higher output

Cost,

Revenue,

Profit

($s per year)

0

Output (units per year)


Marginal revenue marginal cost and profit maximization1

Cost,

Revenue,

Profit

$ (per year)

C(q)

R(q)

A

B

q0

q*

0

Output (units per year)

Marginal Revenue, Marginal Cost,and Profit Maximization

  • Comparing R(q) and C(q)

    • Question: Why is profit negative when output is zero?


Marginal revenue marginal cost and profit maximization2

Cost,

Revenue,

Profit

$ (per year)

C(q)

R(q)

A

B

q0

q*

0

Output (units per year)

Marginal Revenue, Marginal Cost,and Profit Maximization

  • Comparing R(q) and C(q)

    • Output levels: q0 - q*

      • R(q)> C(q)

      • MR > MC

        • Indicates higher profit at higher output

        • Profit is increasing


Marginal revenue marginal cost and profit maximization3

Cost,

Revenue,

Profit

$ (per year)

C(q)

R(q)

A

B

q0

q*

0

Output (units per year)

Marginal Revenue, Marginal Cost,and Profit Maximization

  • Comparing R(q) and C(q)

    • Output level: q*

      • R(q)> C(q)

      • MR = MC

      • Profit is maximized


Marginal revenue marginal cost and profit maximization4

Cost,

Revenue,

Profit

$ (per year)

C(q)

R(q)

A

B

q0

q*

0

Output (units per year)

Marginal Revenue, Marginal Cost,and Profit Maximization

  • Question

    • Why is profit reduced when producing more or less than q*?


Marginal revenue marginal cost and profit maximization5

Cost,

Revenue,

Profit

$ (per year)

C(q)

R(q)

A

B

q0

q*

0

Output (units per year)

Marginal Revenue, Marginal Cost,and Profit Maximization

  • Comparing R(q) and C(q)

    • Output levels beyond q*:

      • R(q)> C(q)

      • MC > MR

      • Profit is decreasing


Marginal revenue marginal cost and profit maximization6

Cost,

Revenue,

Profit

$ (per year)

C(q)

R(q)

A

B

q0

q*

0

Output (units per year)

Marginal Revenue, Marginal Cost,and Profit Maximization

  • Therefore, it can be said:

    • Profits are maximized when MC = MR.


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四、完全竞争厂商的短期均衡和短期供给曲线

  • 在短期,厂商是在给定的生产规模下,通过对产量的调整来实现MR=SMC的利润最大化均衡条件,此时厂商利润可以大于、等于、甚至小于0。

  • 课本PP193,6-6。


A competitive firm making a positive profit

MC

Lost profit for

qq < q*

Lost profit for

q2 > q*

A

D

AR=MR=P

ATC

C

B

AVC

At q*: MR = MC

and P > ATC

q1 : MR > MC and

q2: MC > MR and

q0: MC = MR but

MC falling

q0

q1

q*

q2

A Competitive Firm Making a Positive Profit

Price

($ per

unit)

60

50

40

30

20

10

0

1

2

3

4

5

6

7

8

9

10

11

Output


A competitive firm incurring losses

MC

ATC

B

C

D

P = MR

A

At q*: MR = MC

and P < ATC

Losses =(P- AC) x q* or ABCD

AVC

F

E

q*

A Competitive Firm Incurring Losses

Price

($ per

unit)

Would this producer

continue to produce with a loss?

Output


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四、完全竞争厂商的短期均衡和短期供给曲线

  • 供给曲线:

    • 完全竞争厂商的供给曲线可以用SMC曲线来表示,这是因为在完全竞争市场中,P=MR=MC(Q)。它表示厂商在每一个价格水平的供给量,这一供给量给厂商带来最大利润或最小亏损。

    • 厂商只有在 的情况下才会进行生产,因此厂商的短期供给曲线是SMC曲线上大于和等于AVC曲线最低点的部分来表示。


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供给曲线


Consumer and producer surplus

10

Consumer

Surplus

S

7

Between 0 and Q0

consumers A and B

receive a net gain from

buying the product--

consumer surplus

5

Producer

Surplus

Between 0 and Q0

producers receive

a net gain from

selling each product--

producer surplus.

D

Q0

Consumer A

Consumer B

Consumer C

Consumer and Producer Surplus

生产者剩余:

Price

0

Quantity


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S

The short-run

industry supply curve

is the horizontal

summation of the supply

curves of the firms.

MC1

MC2

MC3

P3

P2

P1

五、完全竞争行业的短期供给曲线

$ per

unit

Quantity

0

2

4

5

7

8

10

15

21


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六、完全竞争厂商的长期均衡

  • 厂商在长期生产中对全部生产要素的调整可以表现为两个方面:

    • 对最优生产规模的选择;

    • 进入或退出一个行业的决策。

  • 长期利润最大化条件:MR=LMC

    • 完全竞争厂商的长期均衡出现在LAC曲线的最低点,此时生产的平均成本降到长期平均成本最低点,商品价格等于这个最低长期平均成本点。

    • 长期均衡条件:P=AR=MR=LMC=SMC=LAC=SAC


Output choice in the long run

In the long run, the plant size will be

increased and output increased to q3.

Long-run profit, EFGD > short run

profit ABCD.

LMC

LAC

SMC

SAC

D

A

E

$40

P = MR

C

B

G

F

$30

In the short run, the

firm is faced with fixed

inputs. P = $40 > ATC.

Profit is equal to ABCD.

q1

q2

q3

Output Choice in the Long Run

Price

($ per

unit of

output)

Output


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七、完全竞争行业的长期供给曲线

  • 成本不变行业:

    • 产量变化引起的生产要素需求的变化不对生产要素价格发生影响。该行业的长期供给曲线是一条水平线。

  • 成本递增行业:

    • 产量增加引起的生产要素需求的增加会导致生产要素价格上升。该行业的长期供给曲线是一条向右上方倾斜的曲线。

  • 成本递减行业:

    • 产量增加引起的生产要素需求的增加反而导致生产要素价格下降。该行业的长期供给曲线是一条向右下方倾斜的曲线。


Long run supply in a constant cost industry

Economic profits attract new

firms. Supply increases to S2 and

the market returns to long-run

equilibrium.

Q1 increase to Q2.

Long-run supply = SL = LRAC.

Change in output has no impact on

input cost.

S1

S2

MC

AC

C

P2

P2

A

B

SL

P1

P1

D1

D2

q1

q2

Q1

Q2

Long-Run Supply in aConstant-Cost Industry

$ per

unit of

output

$ per

unit of

output

Output

Output


Long run supply in an increasing cost industry

Due to the increase

in input prices, long-run

equilibrium occurs at

a higher price.

S1

S2

LAC2

SMC2

SL

SMC1

P2

LAC1

P2

P3

P3

B

A

P1

P1

D1

D1

q1

q2

Q1

Q2

Q3

Long-Run Supply in anIncreasing-Cost Industry

$ per

unit of

output

$ per

unit of

output

Output

Output


Long run supply in an decreasing cost industry

Due to the decrease

in input prices, long-run

equilibrium occurs at

a lower price.

S1

S2

SMC1

LAC1

SMC2

P2

P2

LAC2

P1

A

P1

B

P3

P3

SL

D1

D2

q1

q2

Q1

Q2

Q3

Long-Run Supply in anDecreasing-Cost Industry

$ per

unit of

output

$ per

unit of

output

Output

Output


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八、完全竞争市场的短期均衡和长期均衡

  • 均衡的实现:

    • 消费者效用最大化追求消费者需求曲线市场需求曲线

    • 厂商利润最大化追求厂商短期供给曲线市场供给曲线

      竞争市场均衡点E

  • 消费者统治:

    • 在一个经济社会中消费者在商品生产这一基本经济问题上起到决定性的作用,这种作用表现为消费者用货币购买商品等同于向商品投“货币选票”,而厂商为获得最大利润,只能根据货币选票的情况来安排生产。


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