2. Production Decisions in a Perfectly Competitive Market Chapter 6

3. Production Cost Production decisions in a perfectly competitive market

4. Production decisions in other market structures Monopoly Monopolistic Competition Oligopoly

5. Perfect Competition Perfectly competitive market: all participants are price-takers Perfectly competitive industry: all producers are price-takers Price-taker: whose action has no effect on market price Price-taking producer: market price does not change because of the quantity he sells. Price-taking consumer: market price does not change because of the amount he buys.

6. Perfect Competition: Characteristics Many buyers and sellers and each is so small that no one can affect price individually (for sellers, no one has large enough market share) All firms produce a homogeneous product (identical / standardized) at least consumers think so Free entry and exit each firm has complete knowledge about production and cost ； no regulation limit

7. Producer Decision-Making: Goal: Maximize Profit  = TR – TC –TC = TFC + TVC = wL + rK –ATC = TC / Q –MC = Δ(TC)/ΔQ

8. Recall: Short-Run Costs - Summary at Q=0, VC=0, but FC>0 when MC is declining, ATC and AVC both decline at an increasing rate when MC starts increasing, ATC and AVC may both be decreasing but at a decreasing rate MC intersects AVC and ATC at their minimum, respectively

9. The Relationship Between the Average Total Cost and the Marginal Cost Curves

10. the four curves together:

11. More Realistic Cost Curves

12. Total Revenue: TR TR = PQ AR = PQ/Q = P MR = Δ(PQ)/ΔQ = (ΔP*Q)/ΔQ + (P*ΔQ)/ΔQ = (ΔP /ΔQ ) Q + P(ΔQ/ΔQ ) = (ΔP /ΔQ ) Q + P Perfect competition: MR = P = AR (ΔP =0)

13. Short-Run optimal output level in a perfectly competitive market Goal: maximize profit –Demand facing the industry: downward sloping –Demand facing the firm: horizontal at P (all are price takers, and no one is large enough to affect market price) Optimal output level determined by D=P=MR=MC

14. Profit-Maximizing Output Decision rule:  is maximized when MR = MC (think: why?) profit is maximized at the quantity of output where the marginal revenue of the last unit produced is equal to its marginal cost.

15. Short-Run Costs for Jennifer and Jason’s Farm

16. Questions to consider: How much is fixed cost? Is marginal cost calculated based on total cost or variable cost? Why is marginal revenue constant at $18? What is net gain? Is the goal to maximize net gain?

17. Again: under perfect competition MR = Δ(PQ)/ΔQ = (ΔP*Q)/ΔQ + (P*ΔQ)/ΔQ = (ΔP /ΔQ ) Q + P(ΔQ/ΔQ ) When ΔP=0 (price taking)  MR =P Decision rule:  is maximized when MR=P=MC

18. The Price-Taking Firm’s Profit-Maximizing Quantity of Output The profit-maximizing point is where the marginal cost curve crosses the marginal revenue curve (which is a horizontal line at the market price).

19. Profitability and Market Price

20. Costs and Production in the Short-Run

21. Profitability and Market Price

22. The Short-Run Production Decision A firm will cease production in the short-run if the market price falls below the shut-down price, which is equal to minimum average variable cost.

23. Short-Run optimal output level: various profit situations Rule: produce at MR=P=MC. –Positive Economic Profit: when D=MR=P>ATC at MR=P=MC –Operating at a loss: when AVC<D=MR=P<ATC at MR=P=MC –Shut Down: when D=MR=P<AVC at MR=P=MC The break-even price: the market price at which the firm earns zero profit (P=ATC).

24. P Q ATC MC D=MR=P AVC P1 P2 MR>MC, expand MR<MC, reduce MR=MC, optimal Profit Maximization ： MR=MC

25. Principles: MC tells how much to produce (produce up to the amount where MR=P=MC) ATC tells how much profit or loss is made if the firm decides to produce (profit = (P - ATC) * Q). AVC tells whether to keep producing (keep producing only when P>AVC at P=MC)

26. Summary

27. Employees per day 00040 180120.150520.650 2200240.120640.320 3260360.138760.292 4300480.160880.293 5330600.1821000.303 6350720.2061120.320 7362840.2321240.343 Bottles per day Variable cost ($/day) Average variable cost ($/unit of output) Total cost ($/day) Average total cost ($/unit of output) 0.15 0.10 0.20 0.30 0.40 0.60 1.00 Marginal cost ($/bottle) Table 6.4, P.176 Also example: AVC and ATC

28. The Marginal, Average Variable, and Average Total cost Curves for a Bottle Manufacturer

29. Price = Marginal Cost: The Perfectly Competitive Firm’s Profit-Maximizing Supply Rule

30. Measuring Profit Graphically Figure 6.7, P.178

31. A Negative Profit Figure 6.8, P.179

32. The Short-Run Supply A firm will cease production in the short-run if the market price falls below the shut-down price, which is equal to minimum average variable cost.

33. Short-Run Supply for the firm: supply curve is upward sloping because of the law of increasing cost (S=MC). for the industry: the supply curve is upward sloping, flatter than single firm supply curve, and steeper than the horizontal summation firm supplies.

34. The Short-Run Market Equilibrium There is a short-run market equilibrium when the quantity supplied equals the quantity demanded, taking the number of producers as given.

35. The Effect of an Increase in Demand in the Short-Run and the Long-Run D ↑  P ↑  non-zero profits  entry  S ↑  P ↓  back to zero profit (on LRS curve)

36. Comparing the Short-Run and Long-Run Industry Supply Curves The long-run industry supply curve is always flatter—more elastic—than the short-run industry supply curve. This is because of entry and exit:

37. Long-Run optimal output level: All firms will be producing where P=LMC=LAC and economic profit will be zero because of free entry and exit. Firms enjoy big economic rent if they own the resources that have higher productivity than similar resources owned by others.

38. LAC LMC AR=MR E M N O Q P Long-Run Equilibrium

39. The Long-Run Market Equilibrium A market is in long-run market equilibrium when the quantity supplied equals the quantity demanded, given that sufficient time has elapsed for entry into and exit from the industry to occur.

40. Conclusions: In a perfectly competitive industry in equilibrium, the value of marginal cost is the same for all firms. In a perfectly competitive industry with free entry and exit, each firm will have zero economic profits in long- run. The long-run market equilibrium of a perfectly competitive industry is efficient: no mutually beneficial transactions go unexploited.

41. Long-Run Supply: For the firm: produce where P=LMC=min LAC. For a constant-cost industry: long-run supply is horizontal. For an increasing-cost industry: long- run supply is upward sloping.