1. Firms in a Competitive Market 9

2. Big Questions 1.How do competitive markets work? 2.How do firms maximize profits? 3.What does the supply curve look like in perfectly competitive markets?

3. Competitive Markets Competitive markets –Many buyers and sellers –Similar (if not identical) goods –Free entry and exit –Firms are price takers Price taker –Has no control over the market price –“takes” the price as given

4. Economics in Two and a Half Men Alan tries to earn money by entering the competitive industry of personal massage

5. Entry and Exit in I Love Lucy, “The Diner” https://www.yout ube.com/watch? v=doUYH3Uria4 &feature=youtu.b ehttps://www.yout ube.com/watch? v=doUYH3Uria4 &feature=youtu.b e

6. Production and Profits for the Firm Goal of a firm: –Maximize profits –This is true whether the firm is competitive or not A profit maximizing firm needs to consider –Revenues –Costs

7. Profit Maximizing Rule Quantity (Q) –How many driveways did Mr. Plow clear? Price (P) –Price charged per driveway Total Revenue (TR) –TR = P  Q Total Costs (TC) –Sum of all production costs at a certain level of output Profit (π) – π = TR – TC

8. Profit Maximizing Rule Marginal Revenue (MR) –MR = ΔTR ÷ ΔQ –Δ = change in –For a competitive firm, MR = P Marginal Cost (MC) –MC = ΔTC ÷ ΔQ –Additional costs of producing additional units

9. Profit Maximizing Rule Change in Profit –ΔProfit = MR – MC Profit maximizing rule: –To maximize profits, the firm should use a marginal analysis –Profit is maximized by choosing the level of output such that MR = MC

10. Profit Maximizing Rule Profit is maximized by choosing the level of output such that MR = MC If MR > MC –The firm can increase profits by producing more Q If MR < MC –The firm has produced “too much” Q, and profits are not maximized

11. Calculating Profits Quantity TR P  Q TC Profit TR – TC MR Δ TR ÷ Δ Q MC Δ TC ÷ Δ Q Change in Profit MR – MC Δ TR ÷ Δ Q 0$0$250-$250 10100340-240$100$9010 20200410-2101007030 300460-16010050 40400490-901003070 50500510-101002080 60600540601003070 700600100 6040 80800700100 0 90900950-50100250-150 10010001250-250100300-200

12. Sunk Costs Sunk costs –Costs that have been incurred as a result of past decisions –Unrecoverable Sunk-cost fallacy –Considering sunk costs when making new decisions at the margin –Can lead to using out-of-date facilities and incurring large opportunity costs

13. Sunk-Cost Fallacies in Your Life Waiting in line at food court restaurant “A” while there is no line at restaurant “B” –“We might as well stay in line. We’ve already been waiting for 15 minutes.”

14. Sunk Costs in “Three Rivers Stadium Implosion” https://www.yout ube.com/watch? v=gtzQBBJdvjs& feature=youtu.behttps://www.yout ube.com/watch? v=gtzQBBJdvjs& feature=youtu.be

15. Profit Maximization

16. Calculating Profit To find profit, we need to know revenues and costs –For a perfectly competitive firm, revenues can be found by looking at the price (determined by the market) and the quantity sold –Costs are determined by the quantity sold For the firm, Intuition: Profit = (units sold) ×(average profit per unit)

17. The Decision to Shut Down in the Short Run Firms can’t always make a profit –Ski resort in summer –Surf shop in winter Shutting down –Firm will shut down if it cannot cover variable costs –Shutting down is not the same as going out of business and exiting the industry

18. Signaling Profits and losses act as signals to firms Signals –Convey information about the profitability of various markets –Positive profits A signal of profitability. More firms will enter the industry. –Negative profits (losses) A signal that resources could be doing better elsewhere. Firms will exit the industry.

19. When to Operate or Shut Down

20. Profit and Loss in the Short Run ConditionOutcome P > ATCThe firm makes a profit ATC > P > AVC The firm will operate to minimize loss AVC > P The firm will temporarily shut down

21. Short Run Supply Curve

22. Long Run Supply Curve

23. Long Run Shut Down Criteria ConditionOutcome P > ATCThe firm makes a profit P < ATCThe firm should shut down

24. Sunk-Cost Fallacies in Your Life After one semester of college –“I’m not getting much from my experience at Tech, but I’ve already spent time and money for a whole semester here, so I don’t want to transfer to State.”

25. Short Run Market Supply

26. Long Run Market Supply

27. Market in Equilibrium

28. Short Run Adjustment to Demand Decrease

29. Long Run Adjustment to Demand Decrease

30. Animated Analysis Recall that for a competitive industry in the long run: –If firms are making positive profits, then new firms will enter –Profits are a signal for the entry of new firms. The industry will expand –Market supply shifts right  and price will fall until profits are zero

31. Animated Analysis Firm entry caused by positive profits Cost, Price Price Quantity Single FirmMarket D S1S1 MC ATC S2S2 P2P2 P1P1 Q1Q1 Q2Q2

32. Animated Analysis Recall that for a competitive industry in the long run: –If firms are making negative profits, then existing firms will exit –Losses are a signal for the exiting of firms. The industry will contract (shrink) –Market supply shifts left  and price will rise until profits are zero

33. Animated Analysis Firm exit caused by negative profits Cost, Price Price Quantity Single FirmMarket D S1S1 MC ATC S2S2 P2P2 P1P1 Q1Q1 Q2Q2

34. Animated Analysis Summary Free entry means that anyone can enter the industry in response to profit opportunities. Thus, if the industry is profitable, new firms will enter. This increases supply and decreases prices, lowering profits. If the industry is experiencing losses, firms will exit. This decreases supply and increases prices, increasing profits for remaining firms. As long as firms are entering and exiting, we are not in long run equilibrium. In perfect competition, we move toward zero economic profit over time.

35. Long Run Supply Previous graph showed LR supply as horizontal LR supply may be upward-sloping because –Resources may be limited—think about land for farming –Opportunity costs of labor. When expanding production, may have to increase wages to attract more workers