1. Copyright©2004 South-Western 14 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. “Price Taker”

3. Copyright © 2004 South-Western The Revenue of a Competitive Firm Total revenue is proportional to the amount of output. 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.

4. Copyright © 2004 South-Western The Revenue of a Competitive Firm In perfect competition, average revenue equals the price of the good.

5. Copyright © 2004 South-Western The Revenue of a Competitive Firm Marginal revenue is the change in total revenue from an additional unit sold. MR =  TR/  Q For competitive firms, marginal revenue equals the price of the good.

6. Table 1 Total, Average, and Marginal Revenue for a Competitive Firm Copyright©2004 South-Western

7. Table 2 Profit Maximization: A Numerical Example Copyright©2004 South-Western

8. Figure 1 Profit Maximization for a Competitive Firm Copyright © 2004 South-Western Quantity 0 Costs and Revenue MC ATC AVC MC 1 Q 1 2 Q 2 The firm maximizes profit by producing the quantity at which marginal cost equals marginal revenue. Q MAX P = MR 1 = 2 P = AR = MR

9. 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. When MR > MC  increase Q When MR < MC  decrease Q When MR = MC  Profit is maximized.When MR = MC  Profit is maximized.

10. Figure 2 Marginal Cost as the Competitive Firm’s Supply Curve Copyright © 2004 South-Western Quantity 0 Price MC ATC AVC P 1 Q 1 P 2 Q 2 This section of the firm’s MC curve is also the firm’s supply curve.

11. 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.

12. 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

13. 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.

14. 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.

15. 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

16. 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

17. 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

18. 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

19. 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.

20. Figure 5 Profit as the Area between Price and Average Total Cost Copyright © 2004 South-Western (a) A Firm with Profits Quantity 0 Price P=AR= MR ATCMC P ATC Q (profit-maximizing quantity) Profit

21. Figure 5 Profit as the Area between Price and Average Total Cost Copyright © 2004 South-Western (b) A Firm with Losses Quantity 0 Price ATCMC (loss-minimizing quantity) P=AR= MR P ATC Q Loss

22. 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. 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.

23. 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

24. 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.

25. 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

26. 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.

27. 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.

28. 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 P 1 ATC Long-run supply P 1 1 Q A MC

29. Figure 8 An Increase in Demand in the Short Run and Long Run Copyright © 2004 South-Western Market Firm (b) Short-Run Response Quantity (firm) 0 Price MC ATC Profit P 1 Quantity (market) Long-run supply Price 0 D 1 D 2 P 1 S 1 P 2 Q 1 A Q 2 P 2 B

30. Figure 8 An Increase in Demand in the Short Run and Long Run Copyright © 2004 South-Western P 1 Firm (c) Long-Run Response Quantity (firm) 0 Price MC ATC Market Quantity (market) Price 0 P 1 P 2 Q 1 Q 2 Long-run supply B D 1 D 2 S 1 A S 2 Q 3 C