1. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. CHAPTER 6 Perfectly competitive markets

2. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. OUTLINE OUTLINE 6.1 What is a Competitive Market 6.2 The Revenue of a Competitive Firm 6.3 Profit Maximization and the Competitive Firm’s Supply Curve 6.4 The Firm’s Short-Run Decision to Shut Down 6.5 The Long-Run Supply Curve 6.6 Short and Long-run Equilibrium of Perfectly Competitive Market

3. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. u A perfectly competitive market has the following characteristics: u There are many buyers and sellers in the market. u The goods offered by the various sellers are largely the same. u Firms can freely enter or exit the market.6.1 WHAT IS A COMPETITIVE MARKET

4. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. u As a result of its characteristics, the perfectly competitive market has the following outcomes: u The actions of any single buyer or seller in the market have a negligible impact on the market price. u Each buyer and seller takes the market price as given.6.16.1 WHAT IS A COMPETITIVE MARKET

5. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. n A competitive market has many buyers and sellers trading identical products so that each buyer and seller is a price taker. äBuyers and sellers must accept the price determined by the market.6.1 WHAT IS A COMPETITIVE MARKET

6. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. Total revenue for a firm is the selling price times the quantity sold. TR = (P X Q)6.2 The Revenue of a Competitive Firm Total revenue is proportional to the amount of output.

7. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. n Average revenue tells us how much revenue a firm receives for the typical unit sold. n Average revenue is total revenue divided by the quantity sold.6.2 The Revenue of a Competitive Firm

8. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. In perfect competition, average revenue equals the price of the good.6.2 The Revenue of a Competitive Firm

9. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. Marginal revenue is the change in total revenue from an additional unit sold. MR =  TR/  Q6.2 The Revenue of a Competitive Firm For competitive firms, marginal revenue equals the price of the good.

10. Table 1 Total, Average, and Marginal Revenue for a Competitive Firm6.2 The Revenue of a Competitive Firm

11. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. u The goal of a competitive firm is to maximize profit. u This means that the firm will want to produce the quantity that maximizes the difference between total revenue and total cost.6.3 Profit Maximization and the Competitive Firm’s Supply Curve

12. Table 2 Profit Maximization: A Numerical Example Copyright©2004 South-Western6.3 Profit Maximization and the Competitive Firm’s Supply Curve

13. 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 6.3 Profit Maximization and the Competitive Firm’s Supply Curve

14. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. Profit Maximization for the Competitive Firm6.3 Profit Maximization and the Competitive Firm’s Supply Curve When MR > MC  increase Q When MR < MC  decrease Q When MR = MC  Profit is maximized. Profit maximization occurs at the quantity where marginal revenue equals marginal cost.

15. Figure 2 Marginal Cost as the Competitive Firm’s Supply Curve 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. 6.3 Profit Maximization and the Competitive Firm’s Supply Curve

16. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. u A shutdown refers to a short-run decision not to produce anything during a specific period of time because of current market conditions. u Exit refers to a long-run decision to leave the market.6.3 The Firm’s Short-Run Decision to Shut Down

17. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc.6.4 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

18. Figure 3 The Competitive Firm’s Short Run Supply Curve 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. 6.4 The Firm’s Short-Run Decision to Shut Down

19. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc.6.4 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.

20. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc.6.4 The Firm’s Short-Run Decision to Shut Down u 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

21. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc.6.4 The Firm’s Short-Run Decision to Shut Down u 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

22. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. Figure 4 The Competitive Firm’s Long-Run Supply Curve Quantity MC = Long-run S ATC AVC 0 Costs Firm enters if P > ATC Firm exits if P < ATC 6.5 The Long-Run Supply Curve

23. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. THE SUPPLY CURVE IN A COMPETITIVE MARKET6.5 The Long-Run Supply Curve The competitive firm’s long-run supply curve is the portion of its marginal-cost curve that lies above average total cost.

24. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. Figure 4 The Competitive Firm’s Long-Run Supply Curve Quantity MC ATC AVC 0 Costs Firm’s long-run supply curve 6.5 The Long-Run Supply Curve

25. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. THE SUPPLY CURVE IN A COMPETITIVE MARKET u Short-Run Supply Curve u The portion of its marginal cost curve that lies above average variable cost. u Long-Run Supply Curve u The marginal cost curve above the minimum point of its average total cost curve.6.5 The Long-Run Supply Curve

26. Figure 5 Profit as the Area between Price and Average Total Cost (a) A Firm with Profits Quantity 0 Price P=AR= MR ATCMC P ATC Q (profit-maximizing quantity) Profit 6.5 The Long-Run Supply Curve

27. Figure 5 Profit as the Area between Price and Average Total Cost (b) A Firm with Losses Quantity 0 Price ATCMC (loss-minimizing quantity) P=AR= MR P ATC Q Loss 6.5 The Long-Run Supply Curve

28. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. Supply in a Competitive Market Market supply equals the sum of the quantities supplied by the individual firms in the market.6.4 The Long-Run Supply Curve

29. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. The Short Run: Market Supply with a Fixed Number of Firms u For any given price, each firm supplies a quantity of output so that its marginal cost equals price. u The market supply curve reflects the individual firms’ marginal cost curves.6.5 The Long-Run Supply Curve

30. Figure 6 Market Supply with a Fixed Number of Firms (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 6.5 The Long-Run Supply Curve

31. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. The Long Run: Market Supply with Entry and Exit u Firms will enter or exit the market until profit is driven to zero. u In the long run, price equals the minimum of average total cost. u The long-run market supply curve is horizontal at this price.6.5 The Long-Run Supply Curve

32. Figure 7 Market Supply with Entry and Exit (a) Firm’s Zero-Profit Condition Quantity (firm) 0 Price (b) Market Supply Quantity (market) Price 0 P = minimum ATC Supply MC ATC 6.5 The Long-Run Supply Curve

33. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. The Long Run: Market Supply with Entry and Exit u At the end of the process of entry and exit, firms that remain must be making zero economic profit. u The process of entry & exit ends only when price and average total cost are driven to equality. u Long-run equilibrium must have firms operating at their efficient scale.6.5 The Long-Run Supply Curve

34. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. Why Do Competitive Firms Stay in Business If They Make Zero Profit? u Profit equals total revenue minus total cost. u Total cost includes all the opportunity costs of the firm. u In the zero-profit equilibrium, the firm’s revenue compensates the owners for the time and money they expend to keep the business going.6.5 The Long-Run Supply Curve

35. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. A Shift in Demand in the Short Run and Long Run u An increase in demand raises price and quantity in the short run. u Firms earn profits because price now exceeds average total cost.6.6 Short and long-run equilibrium of perfectly competitive market

36. 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 6.6 Short and long-run equilibrium of perfectly competitive market

37. Figure 8 An Increase in Demand in the Short Run and Long Run 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 6.6 Short and long-run equilibrium of perfectly competitive market

38. Figure 8 An Increase in Demand in the Short Run and Long Run 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 6.6 Short and long-run equilibrium of perfectly competitive market

39. Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc. Why the Long-Run Supply Curve Might Slope Upward u Some resources used in production may be available only in limited quantities. u Firms may have different costs. Marginal Firm äThe marginal firm is the firm that would exit the market if the price were any lower. 6.6 Short and long-run equilibrium of perfectly competitive market