1. Firms in Competitive Markets
Chapter 14

2. Competitive Market
Lots of buyers and sellers dealing in identical goods.
Sellers can freely enter or leave.

3. Firms in a competitive market …
… are price takers. They take the price as given because nothing they do can affect it.
For a firm in a competitive market, the price is the marginal revenue.

4. Profit maximization assumption
Firms act to maximize profit (Π ).
Profit = total revenue – total cost
= PQ – FC – VC

5. Profit maximization exampleQ TR TC Π MR MC ΔΠ 3
(3) 6 1 5 2 4 12 8 18 24 17 7 30 23 36
(1) 42 38
(2) 48 47 9

6. Rule for profit maximization
If MC is rising, produce up to the point at which MC = MR.

7. Figure 1 Profit Maximization for a Competitive Firm
Costs
The firm maximizes
profit by producing
the quantity at which
marginal cost equals
marginal revenue.
and
Revenue MC MC 2 Q
ATC P = MR 1 2 AR Q
MAX
AVC MC 1 Q
Quantity
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8. Figure 2 Marginal Cost as the Competitive Firm’s Supply Curve
Price
This section of the
firm’s MC curve is
also the firm’s supply
curve. MC P 2 Q
ATC P 1 Q
AVC
Quantity
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9. Figure 3 The Competitive Firm’s Short Run Supply Curve
Costs
Firm ’
s short-run
supply curve
If P > ATC, the firm will continue to produce at a profit. MC
ATC
If P > AVC, firm will continue to produce in the short run.
AVC
Firm
shuts
down if P
<
AVC
Quantity
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10. Shutdown vs. Exit
A shutdown refers to a short-run decision not to produce anything during a specific period of time.
Exit refers to a long-run decision to leave the market.

11. Figure 4 The Competitive Firm’s Long-Run Supply Curve
Costs
Firm ’
s long-run
supply curve
MC = long-run S
Firm
enters if
P > ATC
ATC
Firm
exits if
P < ATC
Quantity
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12. Figure 5 Profit as the Area between Price and Average Total Cost
(a) A Firm with Profits
Price
ATC MC
Profit
ATC Q P P = AR MR
Quantity
(profit-maximizing quantity)
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13. Figure 5 Profit as the Area between Price and Average Total Cost
(b) A Firm with Losses
Price MC
ATC
ATC Q
Loss P = AR MR
Quantity
(loss-minimizing quantity)
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14. Figure 6 Market Supply with a Fixed Number of Firms
(a) Individual Firm Supply
(b) Market Supply
Price
Price MC
Supply
$2.00
200
$2.00
200,000
1.00
100
1.00
100,000
Quantity (firm)
Quantity (market)
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15. Figure 7 Market Supply with Entry and Exit
(a) Firm ’
s Zero-Profit Condition
(b) Market Supply
Price
Price MC
ATC P
= minimum
ATC
Supply
Quantity (firm)
Quantity (market)
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16. Figure 8 An Increase in Demand in the Short Run and Long Run
(a) Initial Condition
Firm
Market
Price
Price
ATC MC S
Short-run supply, 1 D
Demand, 1 1 Q A P 1
Long-run
supply P 1
Quantity (firm)
Quantity (market)

17. Figure 8 An Increase in Demand in the Short Run and Long Run
(b) Short-Run Response
Firm
Market
Price
Price D 2
ATC MC
Profit S 1 Q 2 P B P 2 D 1 Q 1 A P 1 P
Long-run 1
supply
Quantity (firm)
Quantity (market)
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18. Figure 8 An Increase in Demand in the Short Run and Long Run
(c) Long-Run Response
Firm
Market
Price
Price D 2 S MC
ATC 1 S 2 B P 2 A Q 3 C P 1 P
Long-run 1
supply D 1
Quantity (firm) Q Q
Quantity (market) 1 2
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