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Copyright©2004 South-Western
1414Firms in Competitive
Markets
Copyright © 2004 South-Western
WHAT IS A COMPETITIVE
MARKET?
• A perfectly competitive market has the
following characteristics:
• There are many buyers and sellers in the market.
• The goods offered by the various sellers are largely
the same.
• Firms can freely enter or exit the market.
Copyright © 2004 South-Western
WHAT IS A COMPETITIVE
MARKET?
• As a result of its characteristics, the perfectly
competitive market has the following
outcomes:
• The actions of any single buyer or seller in the
market have a negligible impact on the market
price.
• Each buyer and seller takes the market price as
given.
Copyright © 2004 South-Western
WHAT IS A COMPETITIVE
MARKET?
• A competitive market has many buyers and
sellers trading identical products so that each
buyer and seller is a price taker.
• Buyers and sellers must accept the price determined
by the market.
Copyright © 2004 South-Western
The Revenue of a Competitive Firm
• Total revenue for a firm is the selling price
times the quantity sold.
TR = (PTR = (P ×× Q)Q)
Copyright © 2004 South-Western
The Revenue of a Competitive Firm
• Total revenue is proportional to the amount of
output.
Copyright © 2004 South-Western
The Revenue of a Competitive Firm
• Average revenue tells us how much revenue a
firm receives for the typical unit sold.
• Average revenue is total revenue divided by the
quantity sold.
Copyright © 2004 South-Western
The Revenue of a Competitive Firm
• In perfect competition, average revenue equals
the price of the good.
A v e r a g e R e v e n u e =
T o t a l r e v e n u e
Q u a n t i t y
P r i c e Q u a n t i t y
Q u a n t i t y
P r i c e
=
×
=
Copyright © 2004 South-Western
The Revenue of a Competitive Firm
• Marginal revenue is the change in total revenue
from an additional unit sold.
MR =MR =∆∆TR/TR/ ∆∆QQ
Copyright © 2004 South-Western
The Revenue of a Competitive Firm
• For competitive firms, marginal revenue equals
the price of the good.
Table 1 Total, Average, and Marginal Revenue for a
Competitive Firm
Copyright©2004 South-Western
Copyright © 2004 South-Western
PROFIT MAXIMIZATION AND THE
COMPETITIVE FIRM’S SUPPLY CURVE
• The goal of a competitive firm is to maximize
profit.
• This means that the firm will want to produce
the quantity that maximizes the difference
between total revenue and total cost.
Table 2 Profit Maximization: A Numerical Example
Copyright©2004 South-Western
Figure 1 Profit Maximization for a Competitive Firm
Copyright © 2004 South-Western
Quantity0
Costs
and
Revenue
MC
ATC
AVC
MC1
Q1
MC2
Q2
The firm maximizes
profit by producing
the quantity at which
marginal cost equals
marginal revenue.
QMAX
P = MR1 = MR2 P = AR = MR
Copyright © 2004 South-Western
PROFIT MAXIMIZATION AND THE
COMPETITIVE FIRM’S SUPPLY CURVE
• Profit maximization occurs at the quantity
where marginal revenue equals marginal cost.
Copyright © 2004 South-Western
PROFIT MAXIMIZATION AND THE
COMPETITIVE FIRM’S SUPPLY CURVE
• When MR > MC increase Q
• When MR < MC decrease Q
• WhenWhen MR = MCMR = MC Profit is maximizedProfit is maximized..
Figure 2 Marginal Cost as the Competitive Firm’s Supply
Curve
Copyright © 2004 South-Western
Quantity0
Price
MC
ATC
AVC
P1
Q1
P2
Q2
This section of the
firm’s MC curve is
also the firm’s supply
curve.
Copyright © 2004 South-Western
The Firm’s Short-Run Decision to Shut Down
• A shutdown refers to a short-run decision not to
produce anything during a specific period of
time because of current market conditions.
• Exit refers to a long-run decision to leave the
market.
Copyright © 2004 South-Western
The Firm’s Short-Run Decision to Shut Down
• The firm considers its sunk costs when deciding
to exit, but ignores them when deciding
whether to shut down.
• Sunk costs are costs that have already been
committed and cannot be recovered.
Copyright © 2004 South-Western
The Firm’s Short-Run Decision to Shut Down
• The firm shuts down if the revenue it gets from
producing is less than the variable cost of
production.
• Shut down if TR < VC
• Shut down if TR/Q < VC/Q
• Shut down if P < AVC
Figure 3 The Competitive Firm’s Short Run Supply Curve
Copyright © 2004 South-Western
MC
Quantity
ATC
AVC
0
Costs
Firm
shuts
down if
P<AVC
Firm’s short-run
supply curve
If P > AVC, firm will
continue to produce
in the short run.
If P > ATC, the firm
will continue to
produce at a profit.
Copyright © 2004 South-Western
The Firm’s Short-Run Decision to Shut Down
• The portion of the marginal-cost curve that lies
above average variable cost is the competitive
firm’s short-run supply curve.
Copyright © 2004 South-Western
The Firm’s Long-Run Decision to Exit or
Enter a Market
• In the long run, the firm exits if the revenue it
would get from producing is less than its total
cost.
• Exit if TR < TC
• Exit if TR/Q < TC/Q
• Exit if P < ATC
Copyright © 2004 South-Western
The Firm’s Long-Run Decision to Exit or
Enter a Market
• A firm will enter the industry if such an action
would be profitable.
• Enter if TR > TC
• Enter if TR/Q > TC/Q
• Enter if P > ATC
Figure 4 The Competitive Firm’s Long-Run Supply Curve
Copyright © 2004 South-Western
MC = long-run S
Firm
exits if
P < ATC
Quantity
ATC
0
Costs
Firm’s long-run
supply curve
Firm
enters if
P > ATC
Copyright © 2004 South-Western
THE SUPPLY CURVE IN A
COMPETITIVE MARKET
• The competitive firm’s long-run supply curvelong-run supply curve is
the portion of its marginal-cost curve that lies
above average total cost.
Figure 4 The Competitive Firm’s Long-Run Supply Curve
Copyright © 2004 South-Western
MC
Quantity
ATC
0
Costs
Firm’s long-run
supply curve
Copyright © 2004 South-Western
THE SUPPLY CURVE IN A
COMPETITIVE MARKET
• Short-Run Supply Curve
• The portion of its marginal cost curve that lies
above average variable cost.
• Long-Run Supply Curve
• The marginal cost curve above the minimum point
of its average total cost curve.
Figure 5 Profit as the Area between Price and Average
Total Cost
Copyright © 2004 South-Western
(a) A Firm with Profits
Quantity0
Price
P = AR = MR
ATCMC
P
ATC
Q
(profit-maximizing quantity)
Profit
Figure 5 Profit as the Area between Price and Average
Total Cost
Copyright © 2004 South-Western
(b) A Firm with Losses
Quantity0
Price
ATCMC
(loss-minimizing quantity)
P = AR = MRP
ATC
Q
Loss
Copyright © 2004 South-Western
THE SUPPLY CURVE IN A
COMPETITIVE MARKET
• Market supply equals the sum of the quantities
supplied by the individual firms in the market.
Copyright © 2004 South-Western
The Short Run: Market Supply with a Fixed
Number of Firms
• For any given price, each firm supplies a
quantity of output so that its marginal cost
equals price.
• The market supply curve reflects the individual
firms’ marginal cost curves.
Figure 6 Market Supply with a Fixed Number of Firms
Copyright © 2004 South-Western
(a) Individual Firm Supply
Quantity (firm)0
Price
MC
1.00
100
$2.00
200
(b) Market Supply
Quantity (market)0
Price
Supply
1.00
100,000
$2.00
200,000
Copyright © 2004 South-Western
The Long Run: Market Supply with Entry and
Exit
• Firms will enter or exit the market until profit is
driven to zero.
• In the long run, price equals the minimum of
average total cost.
• The long-run market supply curve is horizontal
at this price.
Figure 7 Market Supply with Entry and Exit
Copyright © 2004 South-Western
(a) Firm’s Zero-Profit Condition
Quantity (firm)0
Price
(b) Market Supply
Quantity (market)
Price
0
P = minimum
ATC
Supply
MC
ATC
Copyright © 2004 South-Western
The Long Run: Market Supply with Entry and
Exit
• At the end of the process of entry and exit,
firms that remain must be making zero
economic profit.
• The process of entry and exit ends only when
price and average total cost are driven to
equality.
• Long-run equilibrium must have firms
operating at their efficient scale.
Copyright © 2004 South-Western
Why Do Competitive Firms Stay in Business
If They Make Zero Profit?
• Profit equals total revenue minus total cost.
• Total cost includes all the opportunity costs of
the firm.
• In the zero-profit equilibrium, the firm’s
revenue compensates the owners for the time
and money they expend to keep the business
going.
Copyright © 2004 South-Western
A Shift in Demand in the Short Run and
Long Run
• An increase in demand raises price and quantity
in the short run.
• Firms earn profits because price now exceeds
average total cost.
Figure 8 An Increase in Demand in the Short Run and Long
Run
Firm
(a) Initial Condition
Quantity (firm)0
Price
Market
Quantity (market)
Price
0
DDemand, 1
SShort-run supply, 1
P1
ATC
Long-run
supply
P1
1Q
A
MC
Figure 8 An Increase in Demand in the Short Run and Long
Run
Copyright © 2004 South-Western
MarketFirm
(b) Short-Run Response
Quantity (firm)0
Price
MC ATCProfit
P1
Quantity (market)
Long-run
supply
Price
0
D1
D2
P1
S1
P2
Q1
A
Q2
P2
B
Figure 8 An Increase in Demand in the Short Run and Long
Run
Copyright © 2004 South-Western
P1
Firm
(c) Long-Run Response
Quantity (firm)0
Price
MC ATC
Market
Quantity (market)
Price
0
P1
P2
Q1 Q2
Long-run
supply
B
D1
D2
S1
A
S2
Q3
C
Copyright © 2004 South-Western
Why the Long-Run Supply Curve Might
Slope Upward
• Some resources used in production may be
available only in limited quantities.
• Firms may have different costs.
Copyright © 2004 South-Western
Why the Long-Run Supply Curve Might
Slope Upward
• Marginal Firm
• The marginal firm is the firm that would exit the
market if the price were any lower.
Copyright © 2004 South-Western
Summary
• Because a competitive firm is a price taker, its
revenue is proportional to the amount of output
it produces.
• The price of the good equals both the firm’s
average revenue and its marginal revenue.
Copyright © 2004 South-Western
Summary
• To maximize profit, a firm chooses the quantity
of output such that marginal revenue equals
marginal cost.
• This is also the quantity at which price equals
marginal cost.
• Therefore, the firm’s marginal cost curve is its
supply curve.
Copyright © 2004 South-Western
Summary
• 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.
• 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.
Copyright © 2004 South-Western
Summary
• 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.
• Changes in demand have different effects over
different time horizons.
• In the long run, the number of firms adjusts to
drive the market back to the zero-profit
equilibrium.

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Congress in Action
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Congress
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Interest Groups
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The Electoral Process
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Voters and Voter Behavior
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Political Parties
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Federalism
FederalismFederalism
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The Constitution
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The Constitution
 
Origins of American Government
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Principles of Government
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Environmental Policy
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Environmental Policy
 
Foreign and Military Policy
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Social Welfare
Social WelfareSocial Welfare
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Firms in Competitive Markets

  • 2. Copyright © 2004 South-Western WHAT IS A COMPETITIVE MARKET? • A perfectly competitive market has the following characteristics: • There are many buyers and sellers in the market. • The goods offered by the various sellers are largely the same. • Firms can freely enter or exit the market.
  • 3. Copyright © 2004 South-Western WHAT IS A COMPETITIVE MARKET? • As a result of its characteristics, the perfectly competitive market has the following outcomes: • The actions of any single buyer or seller in the market have a negligible impact on the market price. • Each buyer and seller takes the market price as given.
  • 4. Copyright © 2004 South-Western WHAT IS A COMPETITIVE MARKET? • A competitive market has many buyers and sellers trading identical products so that each buyer and seller is a price taker. • Buyers and sellers must accept the price determined by the market.
  • 5. Copyright © 2004 South-Western The Revenue of a Competitive Firm • Total revenue for a firm is the selling price times the quantity sold. TR = (PTR = (P ×× Q)Q)
  • 6. Copyright © 2004 South-Western The Revenue of a Competitive Firm • Total revenue is proportional to the amount of output.
  • 7. Copyright © 2004 South-Western The Revenue of a Competitive Firm • Average revenue tells us how much revenue a firm receives for the typical unit sold. • Average revenue is total revenue divided by the quantity sold.
  • 8. Copyright © 2004 South-Western The Revenue of a Competitive Firm • In perfect competition, average revenue equals the price of the good. A v e r a g e R e v e n u e = T o t a l r e v e n u e Q u a n t i t y P r i c e Q u a n t i t y Q u a n t i t y P r i c e = × =
  • 9. Copyright © 2004 South-Western The Revenue of a Competitive Firm • Marginal revenue is the change in total revenue from an additional unit sold. MR =MR =∆∆TR/TR/ ∆∆QQ
  • 10. Copyright © 2004 South-Western The Revenue of a Competitive Firm • For competitive firms, marginal revenue equals the price of the good.
  • 11. Table 1 Total, Average, and Marginal Revenue for a Competitive Firm Copyright©2004 South-Western
  • 12. Copyright © 2004 South-Western PROFIT MAXIMIZATION AND THE COMPETITIVE FIRM’S SUPPLY CURVE • The goal of a competitive firm is to maximize profit. • This means that the firm will want to produce the quantity that maximizes the difference between total revenue and total cost.
  • 13. Table 2 Profit Maximization: A Numerical Example Copyright©2004 South-Western
  • 14. Figure 1 Profit Maximization for a Competitive Firm Copyright © 2004 South-Western Quantity0 Costs and Revenue MC ATC AVC MC1 Q1 MC2 Q2 The firm maximizes profit by producing the quantity at which marginal cost equals marginal revenue. QMAX P = MR1 = MR2 P = AR = MR
  • 15. Copyright © 2004 South-Western PROFIT MAXIMIZATION AND THE COMPETITIVE FIRM’S SUPPLY CURVE • Profit maximization occurs at the quantity where marginal revenue equals marginal cost.
  • 16. Copyright © 2004 South-Western PROFIT MAXIMIZATION AND THE COMPETITIVE FIRM’S SUPPLY CURVE • When MR > MC increase Q • When MR < MC decrease Q • WhenWhen MR = MCMR = MC Profit is maximizedProfit is maximized..
  • 17. Figure 2 Marginal Cost as the Competitive Firm’s Supply Curve Copyright © 2004 South-Western Quantity0 Price MC ATC AVC P1 Q1 P2 Q2 This section of the firm’s MC curve is also the firm’s supply curve.
  • 18. Copyright © 2004 South-Western The Firm’s Short-Run Decision to Shut Down • A shutdown refers to a short-run decision not to produce anything during a specific period of time because of current market conditions. • Exit refers to a long-run decision to leave the market.
  • 19. Copyright © 2004 South-Western The Firm’s Short-Run Decision to Shut Down • The firm considers its sunk costs when deciding to exit, but ignores them when deciding whether to shut down. • Sunk costs are costs that have already been committed and cannot be recovered.
  • 20. Copyright © 2004 South-Western The Firm’s Short-Run Decision to Shut Down • The firm shuts down if the revenue it gets from producing is less than the variable cost of production. • Shut down if TR < VC • Shut down if TR/Q < VC/Q • Shut down if P < AVC
  • 21. Figure 3 The Competitive Firm’s Short Run Supply Curve Copyright © 2004 South-Western MC Quantity ATC AVC 0 Costs Firm shuts down if P<AVC Firm’s short-run supply curve If P > AVC, firm will continue to produce in the short run. If P > ATC, the firm will continue to produce at a profit.
  • 22. Copyright © 2004 South-Western The Firm’s Short-Run Decision to Shut Down • The portion of the marginal-cost curve that lies above average variable cost is the competitive firm’s short-run supply curve.
  • 23. Copyright © 2004 South-Western The Firm’s Long-Run Decision to Exit or Enter a Market • In the long run, the firm exits if the revenue it would get from producing is less than its total cost. • Exit if TR < TC • Exit if TR/Q < TC/Q • Exit if P < ATC
  • 24. Copyright © 2004 South-Western The Firm’s Long-Run Decision to Exit or Enter a Market • A firm will enter the industry if such an action would be profitable. • Enter if TR > TC • Enter if TR/Q > TC/Q • Enter if P > ATC
  • 25. Figure 4 The Competitive Firm’s Long-Run Supply Curve Copyright © 2004 South-Western MC = long-run S Firm exits if P < ATC Quantity ATC 0 Costs Firm’s long-run supply curve Firm enters if P > ATC
  • 26. Copyright © 2004 South-Western THE SUPPLY CURVE IN A COMPETITIVE MARKET • The competitive firm’s long-run supply curvelong-run supply curve is the portion of its marginal-cost curve that lies above average total cost.
  • 27. Figure 4 The Competitive Firm’s Long-Run Supply Curve Copyright © 2004 South-Western MC Quantity ATC 0 Costs Firm’s long-run supply curve
  • 28. Copyright © 2004 South-Western THE SUPPLY CURVE IN A COMPETITIVE MARKET • Short-Run Supply Curve • The portion of its marginal cost curve that lies above average variable cost. • Long-Run Supply Curve • The marginal cost curve above the minimum point of its average total cost curve.
  • 29. Figure 5 Profit as the Area between Price and Average Total Cost Copyright © 2004 South-Western (a) A Firm with Profits Quantity0 Price P = AR = MR ATCMC P ATC Q (profit-maximizing quantity) Profit
  • 30. Figure 5 Profit as the Area between Price and Average Total Cost Copyright © 2004 South-Western (b) A Firm with Losses Quantity0 Price ATCMC (loss-minimizing quantity) P = AR = MRP ATC Q Loss
  • 31. Copyright © 2004 South-Western THE SUPPLY CURVE IN A COMPETITIVE MARKET • Market supply equals the sum of the quantities supplied by the individual firms in the market.
  • 32. Copyright © 2004 South-Western The Short Run: Market Supply with a Fixed Number of Firms • For any given price, each firm supplies a quantity of output so that its marginal cost equals price. • The market supply curve reflects the individual firms’ marginal cost curves.
  • 33. Figure 6 Market Supply with a Fixed Number of Firms Copyright © 2004 South-Western (a) Individual Firm Supply Quantity (firm)0 Price MC 1.00 100 $2.00 200 (b) Market Supply Quantity (market)0 Price Supply 1.00 100,000 $2.00 200,000
  • 34. Copyright © 2004 South-Western The Long Run: Market Supply with Entry and Exit • Firms will enter or exit the market until profit is driven to zero. • In the long run, price equals the minimum of average total cost. • The long-run market supply curve is horizontal at this price.
  • 35. Figure 7 Market Supply with Entry and Exit Copyright © 2004 South-Western (a) Firm’s Zero-Profit Condition Quantity (firm)0 Price (b) Market Supply Quantity (market) Price 0 P = minimum ATC Supply MC ATC
  • 36. Copyright © 2004 South-Western The Long Run: Market Supply with Entry and Exit • At the end of the process of entry and exit, firms that remain must be making zero economic profit. • The process of entry and exit ends only when price and average total cost are driven to equality. • Long-run equilibrium must have firms operating at their efficient scale.
  • 37. Copyright © 2004 South-Western Why Do Competitive Firms Stay in Business If They Make Zero Profit? • Profit equals total revenue minus total cost. • Total cost includes all the opportunity costs of the firm. • In the zero-profit equilibrium, the firm’s revenue compensates the owners for the time and money they expend to keep the business going.
  • 38. Copyright © 2004 South-Western A Shift in Demand in the Short Run and Long Run • An increase in demand raises price and quantity in the short run. • Firms earn profits because price now exceeds average total cost.
  • 39. Figure 8 An Increase in Demand in the Short Run and Long Run Firm (a) Initial Condition Quantity (firm)0 Price Market Quantity (market) Price 0 DDemand, 1 SShort-run supply, 1 P1 ATC Long-run supply P1 1Q A MC
  • 40. Figure 8 An Increase in Demand in the Short Run and Long Run Copyright © 2004 South-Western MarketFirm (b) Short-Run Response Quantity (firm)0 Price MC ATCProfit P1 Quantity (market) Long-run supply Price 0 D1 D2 P1 S1 P2 Q1 A Q2 P2 B
  • 41. Figure 8 An Increase in Demand in the Short Run and Long Run Copyright © 2004 South-Western P1 Firm (c) Long-Run Response Quantity (firm)0 Price MC ATC Market Quantity (market) Price 0 P1 P2 Q1 Q2 Long-run supply B D1 D2 S1 A S2 Q3 C
  • 42. Copyright © 2004 South-Western Why the Long-Run Supply Curve Might Slope Upward • Some resources used in production may be available only in limited quantities. • Firms may have different costs.
  • 43. Copyright © 2004 South-Western Why the Long-Run Supply Curve Might Slope Upward • Marginal Firm • The marginal firm is the firm that would exit the market if the price were any lower.
  • 44. Copyright © 2004 South-Western Summary • Because a competitive firm is a price taker, its revenue is proportional to the amount of output it produces. • The price of the good equals both the firm’s average revenue and its marginal revenue.
  • 45. Copyright © 2004 South-Western Summary • To maximize profit, a firm chooses the quantity of output such that marginal revenue equals marginal cost. • This is also the quantity at which price equals marginal cost. • Therefore, the firm’s marginal cost curve is its supply curve.
  • 46. Copyright © 2004 South-Western Summary • 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. • 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.
  • 47. Copyright © 2004 South-Western Summary • 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. • Changes in demand have different effects over different time horizons. • In the long run, the number of firms adjusts to drive the market back to the zero-profit equilibrium.