ch利潤最大化和競爭性供給課件

1、CHAPTER 8 OUTLINE8.1Perfectly Competitive Markets8.2Profit Maximization8.3Marginal Revenue, Marginal Cost, and Profit Maximization8.4Choosing Output in the Short Run8.5The Competitive Firms Short-Run Supply Curve8.6The Short-Run Market Supply Curve8.7Choosing Output in the Long Run8.8The Industrys L

2、ong-Run Supply Curve第1頁，共36頁。PERFECTLY COMPETITIVE MARKETS8.1The model of perfect competition rests on three basic assumptions:(1) price taking,(2) product homogeneity, and (3) free entry and exit.Price TakingBecause each individual firm sells a sufficiently small proportion of total market output,

3、its decisions have no impact on market price. price taker Firm that has no influence over market price and thus takes the price as given.Product HomogeneityWhen the products of all of the firms in a market are perfectly substitutable with one anotherthat is, when they are homogeneousno firm can rais

4、e the price of its product above the price of other firms without losing most or all of its business.第2頁，共36頁。PERFECTLY COMPETITIVE MARKETS8.1Free Entry and Exit free entry (or exit) Condition under which there are no special costs that make it difficult for a firm to enter (or exit) an industry.Whe

5、n Is a Market Highly Competitive?Because firms can implicitly or explicitly collude in setting prices, the presence of many firms is not sufficient for an industry to approximate perfect competition. Conversely, the presence of only a few firms in a market does not rule out competitive behavior.第3頁，

6、共36頁。PROFIT MAXIMIZATION8.2Do Firms Maximize Profit?The assumption of profit maximization is frequently used in microeconomics because it predicts business behavior reasonably accurately and avoids unnecessary analytical complications. For smaller firms managed by their owners, profit is likely to d

7、ominate almost all decisions. In larger firms, however, managers who make day-to-day decisions usually have little contact with the owners (i.e. the stockholders).In any case, firms that do not come close to maximizing profit are not likely to survive. Firms that do survive in competitive industries

8、 make long-run profit maximization one of their highest priorities.Alternative Forms of Organizationcooperative Association of businesses or people jointly owned and operated by members for mutual benefit.第4頁，共36頁。PROFIT MAXIMIZATION8.2Nationwide, condos are a far more common than co-ops, outnumberi

9、ng them by a factor of nearly 10 to 1. In this regard, New York City is very different from the rest of the nationco-ops are more popular, and outnumber condos by a factor of about 4 to 1.What accounts for the relative popularity of housing cooperatives in New York City? Part of the answer is histor

10、ical. Housing cooperatives are a much older form of organization in the U.S.The building restrictions in New York have long disappeared, and yet the conversion of apartments from co-ops to condos has been relatively slow.The typical condominium apartment is worth about 15.5 percent more than a equiv

11、alent apartment held in the form of a co-op.It appears that in New York, many owners have been willing to forgo substantial amounts of money in order to achieve non-monetary benefits.第5頁，共36頁。MARGINAL REVENUE, MARGINAL COST,AND PROFIT MAXIMIZATION8.3profit Difference between total revenue and total

12、cost.(q) = R(q) C(q)marginal revenue Change in revenue resulting from a one-unit increase in output.Profit Maximization in the Short RunFigure 8.1A firm chooses output q*, so that profit, the difference AB between revenue R and cost C, is maximized. At that output, marginal revenue (the slope of the

13、 revenue curve) is equal to marginal cost (the slope of the cost curve)./q = R/q C/q = 0MR(q) = MC(q)第6頁，共36頁。MARGINAL REVENUE, MARGINAL COST,AND PROFIT MAXIMIZATION8.3Demand and Marginal Revenue for a Competitive FirmBecause each firm in a competitive industry sells only a small fraction of the ent

14、ire industry output, how much output the firm decides to sell will have no effect on the market price of the product.Because it is a price taker, the demand curve d facing an individual competitive firm is given by a horizontal line.第7頁，共36頁。MARGINAL REVENUE, MARGINAL COST,AND PROFIT MAXIMIZATION8.3

15、Demand and Marginal Revenue for a Competitive FirmDemand Curve Faced by a Competitive FirmFigure 8.2A competitive firm supplies only a small portion of the total output of all the firms in an industry. Therefore, the firm takes the market price of the product as given, choosing its output on the ass

16、umption that the price will be unaffected by the output choice. In (a) the demand curve facing the firm is perfectly elastic, even though the market demand curve in (b) is downward sloping.第8頁，共36頁。MARGINAL REVENUE, MARGINAL COST,AND PROFIT MAXIMIZATION8.3The demand d curve facing an individual firm

17、 in a competitive market is both its average revenue curve and its marginal revenue curve. Along this demand curve, marginal revenue, average revenue, and price are all equal.Profit Maximization by a Competitive FirmMC(q) = MR = P第9頁，共36頁。CHOOSING OUTPUT IN THE SHORT RUN8.4Short-Run Profit Maximizat

18、ion by a Competitive FirmMarginal revenue equals marginal cost at a point at which the marginal cost curve is rising.Output Rule: If a firm is producing any output, it should produce at the level at which marginal revenue equals marginal cost.第10頁，共36頁。CHOOSING OUTPUT IN THE SHORT RUN8.4The Short-Ru

19、n Profit of a Competitive FirmA Competitive Firm Making a Positive ProfitFigure 8.3In the short run, the competitive firm maximizes its profit by choosing an output q* at which its marginal cost MC is equal to the price P (or marginal revenue MR) of its product. The profit of the firm is measured by

20、 the rectangle ABCD. Any change in output, whether lower at q1 or higher at q2, will lead to lower profit.第11頁，共36頁。CHOOSING OUTPUT IN THE SHORT RUN8.4The Short-Run Profit of a Competitive FirmA Competitive Firm Incurring LossesFigure 8.4A competitive firm should shut down if price is below AVC.The

21、firm may produce in the short run if price is greater than average variable cost.Shut-Down Rule: The firm should shut down if the price of the product is less than the average variable cost of production at the profit-maximizing output.第12頁，共36頁。CHOOSING OUTPUT IN THE SHORT RUN8.4How should the mana

22、ger determine the plants profit maximizing output? Recall that the smelting plants short-run marginal cost of production depends on whether it is running two or three shifts per day.The Short-Run Output of an Aluminum Smelting PlantFigure 8.5In the short run, the plant should produce 600 tons per da

23、y if price is above $1140 per ton but less than $1300 per ton. If price is greater than $1300 per ton, it should run an overtime shift and produce 900 tons per day. If price drops below $1140 per ton, the firm should stop producing, but it should probably stay in business because the price may rise

24、in the future.第13頁，共36頁。CHOOSING OUTPUT IN THE SHORT RUN8.4The application of the rule that marginal revenue should equal marginal cost depends on a managers ability to estimate marginal cost.To obtain useful measures of cost, managers should keep three guidelines in mind.First, except under limited

25、 circumstances, average variable cost should not be used as a substitute for marginal cost.Second, a single item on a firms accounting ledger may have two components, only one of which involves marginal cost.Third, all opportunity costs should be included in determining marginal cost.第14頁，共36頁。THE C

26、OMPETITIVE FIRMS SHORT-RUNSUPPLY CURVE8.5The firms supply curve is the portion of the marginal cost curve for which marginal cost is greater than average variable cost.The Short-Run Supply Curve for a Competitive FirmFigure 8.6In the short run, the firm chooses its output so that marginal cost MC is

27、 equal to price as long as the firm covers its average variable cost. The short-run supply curve is given by the crosshatched portion of the marginal cost curve.第15頁，共36頁。THE COMPETITIVE FIRMS SHORT-RUNSUPPLY CURVE8.5The Response of a Firm to a Change in Input PriceFigure 8.7When the marginal cost o

28、f production for a firm increases (from MC1 to MC2),the level of output that maximizes profit falls (from q1 to q2).第16頁，共36頁。THE COMPETITIVE FIRMS SHORT-RUNSUPPLY CURVE8.5Although plenty of crude oil is available, the amount that you refine depends on the capacity of the refinery and the cost of pr

29、oduction.The Short-Run Production of Petroleum ProductsFigure 8.8As the refinery shifts from one processing unit to another, the marginal cost of producing petroleum products from crude oil increases sharply at several levels of output. As a result, the output level can be insensitive to some change

30、s in price but very sensitive to others.第17頁，共36頁。THE SHORT-RUN MARKET SUPPLY CURVE8.6Industry Supply in the Short RunThe short-run industry supply curve is the summation of the supply curves of the individual firms.Because the third firm has a lower average variable cost curve than the first two fi

31、rms, the market supply curve S begins at price P1 and follows the marginal cost curve of the third firm MC3 until price equals P2, when there is a kink. For P2 and all prices above it, the industry quantity supplied is the sum of the quantities supplied by each of the three firms.Figure 8.9Elasticit

32、y of Market SupplyEs = (Q/Q)/(P/P)第18頁，共36頁。THE SHORT-RUN MARKET SUPPLY CURVE8.6Table 8.1 The World Copper Industry (2006)CountryAustraliaCanadaChileIndonesiaPeruPolandRussiaUSZambiaCountry9506005,4008001,0505307201,220540Annual Production(Thousand Metric Tons)Country1.151.300.800.900.851.200.650.85

33、0.75Marginal Cost(Dollars Per Pound)Source for Annual Production Data: U.S. Geological Survey, Mineral Commodity Summaries, January 2007./minerals/pubs/mcs/2007/mcs2007.pdf.Source for Marginal Cost Data: Charles River Associates Estimates.第19頁，共36頁。THE SHORT-RUN MARKET SUPPLY CURVE8.6The Short-Run W

34、orld Supply of CopperThe supply curve for world copper is obtained by summing the marginal cost curves for each of the major copper-producing countries. The supply curve slopes upward because the marginal cost of production ranges from a low of 65 cents in Russia to a high of $1.30 in Canada.Figure

35、8.10第20頁，共36頁。THE SHORT-RUN MARKET SUPPLY CURVE8.6Producer Surplus in the Short Run producer surplus Sum over all units produced by a firm of differences between the market price of a good and the marginal cost of production.Producer Surplus for a FirmThe producer surplus for a firm is measured by t

36、he yellow area below the market price and above the marginal cost curve, between outputs 0 and q*, the profit-maximizing output. Alternatively, it is equal to rectangle ABCD because the sum of all marginal costs up to q* is equal to the variable costs of producing q*.Figure 8.11第21頁，共36頁。THE SHORT-R

37、UN MARKET SUPPLY CURVE8.6Producer Surplus in the Short RunProducer Surplus for a MarketThe producer surplus for a market is the area below the market price and above the market supply curve, between 0 and output Q*.Figure 8.12Producer Surplus versus ProfitProducer surplus = PS = R VCProfit = = R VC

38、FC第22頁，共36頁。CHOOSING OUTPUT IN THE LONG RUN8.7Long-Run Profit MaximizationOutput Choice in the Long RunThe firm maximizes its profit by choosing the output at which price equals long-run marginal cost LMC. In the diagram, the firm increases its profit from ABCD to EFGD by increasing its output in th

39、e long run.Figure 8.13The long-run output of a profit-maximizing competitive firm is the point at which long-run marginal cost equals the price.第23頁，共36頁。CHOOSING OUTPUT IN THE LONG RUN8.7Long-Run Competitive EquilibriumAccounting Profit and Economic Profit = R wL rKZero Economic Profit zero economi

40、c profit A firm is earning a normal return on its investmenti.e., it is doing as well as it could by investing its money elsewhere.第24頁，共36頁。CHOOSING OUTPUT IN THE LONG RUN8.7Long-Run Competitive EquilibriumEntry and ExitLong-Run Competitive EquilibriumInitially the long-run equilibrium price of a p

41、roduct is $40 per unit, shown in (b) as the intersection of demand curve D and supply curve S1. In (a) we see that firms earn positive profits because long-run average cost reaches a minimum of $30 (at q2). Positive profit encourages entry of new firms and causes a shift to the right in the supply c

42、urve to S2, as shown in (b). The long-run equilibrium occurs at a price of $30, as shown in (a), where each firm earns zero profit and there is no incentive to enter or exit the industry.Figure 8.14第25頁，共36頁。CHOOSING OUTPUT IN THE LONG RUN8.7Long-Run Competitive EquilibriumEntry and ExitIn a market

43、with entry and exit, a firm enters when it can earn a positive long-run profit and exits when it faces the prospect of a long-run loss. long-run competitive equilibrium All firms in an industry are maximizing profit, no firm has an incentive to enter or exit, and price is such that quantity supplied

44、 equals quantity demanded.A long-run competitive equilibrium occurs when three conditions hold:All firms in the industry are maximizing profit.2. No firm has an incentive either to enter or exit the industry because all firms are earning zero economic profit.3. The price of the product is such that

45、the quantity supplied by the industry is equal to the quantity demanded by consumers.第26頁，共36頁。CHOOSING OUTPUT IN THE LONG RUN8.7Long-Run Competitive EquilibriumFirms Having Identical CostsTo see why all the conditions for long-run equilibrium must hold, assume that all firms have identical costs. N

46、ow consider what happens if too many firms enter the industry in response to an opportunity for profit. The industry supply curve will shift further to the right, and price will fall.第27頁，共36頁。CHOOSING OUTPUT IN THE LONG RUN8.7Long-Run Competitive EquilibriumFirms Having Different CostsThe Opportuni

47、ty Cost of LandNow suppose that all firms in the industry do not have identical cost curves.The distinction between accounting profit and economic profit is important here. If a patent is profitable, other firms in the industry will pay to use it. The increased value of a patent thus represents an o

48、pportunity cost to the firm that holds it.There are other instances in which firms earning positive accounting profit may be earning zero economic profit. Suppose, for example, that a clothing store happens to be located near a large shopping center. The additional flow of customers can substantiall

49、y increase the stores accounting profit because the cost of the land is based on its historical cost.第28頁，共36頁。CHOOSING OUTPUT IN THE LONG RUN8.7Economic RentIn the long run, in a competitive market, the producer surplus that a firm earns on the output that it sells consists of the economic rent tha

50、t it enjoys from all its scarce inputs.economic rent Amount that firms are willing to pay for an input less the minimum amount necessary to obtain it.Producer Surplus in the Long Run第29頁，共36頁。CHOOSING OUTPUT IN THE LONG RUN8.7Firms Earn Zero Profit in Long-Run EquilibriumIn long-run equilibrium, all

51、 firms earn zero economic profit.In (a), a baseball team in a moderate-sized city sells enough tickets so that price ($7) is equal to marginal and average cost.In (b), the demand is greater, so a $10 price can be charged. The team increases sales to the point at which the average cost of production

52、plus the average economic rent is equal to the ticket price. When the opportunity cost associated with owning the franchise is taken into account, the team earns zero economic profit. Figure 8.15Producer Surplus in the Long Run第30頁，共36頁。THE INDUSTRYS LONG-RUN SUPPLY CURVE8.8Constant-Cost Industrycon

53、stant-cost industry Industry whose long-run supply curve is horizontal.Long-Run Supply in a Constant-Cost IndustryIn (b), the long-run supply curve in a constant-cost industry is a horizontal line SL. When demand increases, initially causing a price rise (represented by a move from point A to point

54、C), the firm initially increases its output from q1 to q2, as shown in (a). But the entry of new firms causes a shift to the right in industry supply. Because input prices are unaffected by the increased output of the industry, entry occurs until the original price is obtained (at point B in (b).Fig

55、ure 8.16The long-run supply curve for a constant-cost industry is, therefore, a horizontal line at a price that is equal to the long-run minimum average cost of production.第31頁，共36頁。THE INDUSTRYS LONG-RUN SUPPLY CURVE8.8Increasing-Cost Industryincreasing-cost industry Industry whose long-run supply

56、curve is upward sloping.Long-Run Supply in an Increasing-Cost IndustryIn (b), the long-run supply curve in an increasing-cost industry is an upward-sloping curve SL. When demand increases, initially causing a price rise, the firms increase their output from q1 to q2 in (a). In that case, the entry o

57、f new firms causes a shift to the right in supply from S1 to S2. Because input prices increase as a result, the new long-run equilibrium occurs at a higher price than the initial equilibrium.Figure 8.17In an increasing-cost industry, the long-run industry supply curve is upward sloping.第32頁，共36頁。THE INDUSTRYS LONG-RUN SUPPLY CURVE8.8Decreasing-Cost Industrydecreasing-cost industry Industry whose long-run supply curve is downward sloping.You have been introduced to industries that have constant, increasing, and decreasing long-run costs.We saw that the supply of coffee is e