经济学原理英文版第十四章PPT

committed and cannot be recovered
Sunk costs should be irrelevant to decisions;
you must pay them regardless of your choice.
FC is a sunk cost: The firm must pay its fixed
6
Profit Maximization
What Q maximizes the firm’s profit? To find the answer,
“Think at the margin.” If increase Q by one unit, revenue rises by MR, cost rises by MC.
3. Firms can freely enter or exit the market.
Because of 1 & 2, each buyer and seller is a
“price taker” – takes the price as given.
CHAPTER 14
FIRMS IN COMPETITIVE MARKETS
The MC curve determines the firm’s Q at any price. Hence, the MC curve is the firm’s supply curve. Q1
CHAPTER 14 FIRMS IN COMPETITIVE MARKETS
Costs
MC P2 MR2
Notice that $20 $10 MR = P
$30 $40 $10 $10
$10
$10
5
$10
$50
$10
5
MR = P for a Competitive Firm
A competitive firm can keep increasing its output
without affecting the market price.
CHAPTER 14
FIRMS IN COMPETITIVE MARKETS
11
Байду номын сангаас
A Firm’s Short-Run Decision to Shut Down
If firm shuts down temporarily,
• revenue falls by TR • costs fall by VC
2
The Revenue of a Competitive Firm
Total revenue (TR) Average revenue (AR) Marginal Revenue (MR):
The change in TR from selling one more unit.
TR = P x Q
Should you have the transmission repaired? Don’t consider $1000 when you make decisions. It is a sunk cost.
CHAPTER 14 FIRMS IN COMPETITIVE MARKETS
15
A Firm’s Long-Run Decision to Exit
At the last minute, the transmission dies. You can pay $600 to have it repaired, or sell the car “as is.” Blue book value is $6500 if transmission works, $5700 if it doesn’t.
So, each one-unit increase in Q causes revenue
to rise by P, i.e., MR = P. MR = P is only true for firms in competitive markets.
CHAPTER 14
FIRMS IN COMPETITIVE MARKETS
A firm that shuts down temporarily must still pay
its fixed costs. A firm that exits the market does not have to pay any costs at all, fixed or variable.
14
Firms in Competitive Markets
PRINCIPLES OF
MICROECONOMICS
FOURTH EDITION
N. G R E G O R Y M A N K I W
PowerPoint® Slides by Ron Cronovich
© 2007 Thomson South-Western, all rights reserved
8
MC and the Firm’s Supply Decision
Rule: MR = MC at the profit-maximizing Q. At Qa, MC < MR. So, increase Q to raise profit. At Qb, MC > MR. So, reduce Q to raise profit. At Q1, MC = MR. P1
Introduction: A Scenario
Three years after graduating, you run your own
business.
You have to decide how much to produce, what
price to charge, how many workers to hire, etc.
CHAPTER 14
Q 0
TR $0
TC $5
Profit MR MC
Profit =
MR – MC
$6 4 2
–$5
$10 $4 1 10 5 10 7 8 6
1 2 3
4 5
10 20 30
40 50
9 15 23
33 45
10 7 10
5
10 12
0 –2
FIRMS IN COMPETITIVE MARKETS
P1
MR
Q2
Q
10
Shutdown vs. Exit
Shutdown:
A short-run decision not to produce anything because of market conditions.
Exit:
A long-run decision to leave the market.
5
$10
$50
4
ACTIVE LEARNING
Answers
Q 0 1 2 3 4
1:
∆TR ∆Q
Fill in the empty spaces of the table.
P $10 $10 $10 $10 $10 TR = P x Q $0 $10 AR = TR Q MR =
n.a.
$10
$10 $10 $10
decision as: Exit if P < ATC
CHAPTER 14
FIRMS IN COMPETITIVE MARKETS
16
A New Firm’s Decision to Enter the Market
In the long run, a new firm will enter the market if
What factors should affect these decisions?
• Your costs (studied in preceding chapter) • How much competition you face
We begin by studying the behavior of firms in
If MR > MC, then increase Q to raise profit.
If MR < MC, then reduce Q to raise profit.
CHAPTER 14
FIRMS IN COMPETITIVE MARKETS
7
Profit Maximization
(continued from earlier exercise) At any Q with MR > MC, increasing Q raises profit. At any Q with MR < MC, reducing Q raises profit.
perfectly competitive markets.
CHAPTER 14
FIRMS IN COMPETITIVE MARKETS
1
Characteristics of Perfect Competition
1. Many buyers and many sellers
2. The goods offered for sale are largely the same.
TR =P AR = Q ∆TR MR = ∆Q
CHAPTER 14
FIRMS IN COMPETITIVE MARKETS
3
ACTIVE LEARNING
Exercise
Q 0 1 2 3 4
1:
Fill in the empty spaces of the table.