(精品)14竞争市场中的厂商.ppt

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1、Chapter 14 Firms In Competitive MarketsIf your local gas station raised the price it charges for gasoline by 20 percent,it would see a large drop in the amount of gasoline it sold.Its customers would quickly switch to buying their gasoline at other gas stations.By contrast,if your local water compan

2、y raised the price of water by 20 percent,it would see only a small decrease in the amount of water it sold.People might water their lawns less often and buy more water-efficient shower heads,but they would be hard pressed to reduce water consumption greatly and would be unlikely to find another sup

3、plier.The difference between the gasoline market and the water market is obvious:There are many firms pumping gasoline,but there is only one firm pumping water.As you might expect,this difference in market structure shapes the pricing and production decisions of the firms that operate in these marke

4、ts.14.1 What Is A Competitive Market?A perfectly competitive market has the following characteristics:1.There are many buyers and sellers in the market.2.The goods offered by the various sellers are largely the same(homogeneous ie identical).3.Firms can freely or exit the market.(there are no barrie

5、rs to entry into or exit from the industry).4.There is perfect knowledge.Firms and buyers are completely informed about the product prices of each firm in the industry.5.The factors of production are completely mobile.14.1 What Is A Competitive Market?As a result of its characteristics,the perfectly

6、 competitive market has the following outcomes:The action of any single buyer or seller in the market have a negligible impact on the market price.Each buyer and seller takes the market price as given.14.1 What Is A Competitive Market?A competitive market has many buyers and sellers trading identica

7、l products so that each buyer and seller is a price taker.Buyers and sellers must accept the price determined by the market.14.1.2 The Revenue of a Competitive FirmTotal revenue for a firm is the selling price times the quantity sold.TR=(PQ)Total revenue is proportional to the amount of the output.A

8、verage revenue tells us how much revenue a firm receives for the typical unit sold.Average revenue is total revenue divided by the quantity sold.14.1.2 The Revenue of a Competitive FirmIn perfect competition,average revenue equals the price of the good.Average Revenue=PriceTotal revenueQuantityPrice

9、 QuantityTotal revenueQuantity14.1.2 The Revenue of a Competitive Firm Marginal revenue is the change in total revenue from an additional unit sold.MR=TR/QFor competitive firms,marginal revenue equals the price of the good.Table 1 Total,Average,and Marginal Revenue for a Competitive FirmQuantityPric

10、eTotal RevenueAverage RevenueMarginal Revenue1 gallon$6$6$6$6 6(Q)(P)(TP=PQ)(AR=TR/Q)(MR=TR/Q)2 6 12 63 6 18 64 6 24 65 6 30 66 6 36 67 6 42 68 6 48 6 6 6 6 6 614.2 Profit Maximization and The Competitive Firms Supply CurveThe goal of competitive firm is to maximize profit.This means that the firm w

11、ill want to produce the quantity that maximizes the difference between total revenue and total cost.Table 2 Profit Maximization:A Numerical ExampleQuantityProfitTotal RevenueChange in ProfitMarginal Revenue0 gallons$0$3 -$3$6$2$4(Q)(TR)(TC)(TR-TC)(MR=TR/Q)(MC=TC/Q)(MR-MC)1 6 5 1Total CostMarginal Co

12、st2 12 8 43 18 12 66 36 30 64 24 17 75 30 23 77 42 38 48 48 47 1 6 3 3 6 4 2 6 7 -1 6 8 -2 6 9 -3 6 5 1 6 6 0Figure 1 Profit Maximization for a Competitive FirmCopyright 2004 South-WesternQuantity0CostsandRevenueMCATCAVCMC1Q1MC2Q2The firm maximizesprofit by producing the quantity at whichmarginal co

13、st equalsmarginal revenue.QMAX P=MR1=MR2 P=AR=MRCosts and RevenueQuantity0Q1P=MR1=MR2QMAXQ2MC1MC2P=AR=MRMCATCAVCThe firm maximizes profit by producing the quantity at which marginal cost equals marginal revenue.Figure 14-1.Profit Maximization for a Competitive Firm Figure 14-1.Profit Maximization fo

14、r a Competitive Firm This figure shows the marginal-cost curve(MC),the average-total-cost(ATC),and the average-variable-cost(AVC).It also shows the market price(P),which equals marginal revenue(MR)and average revenue(AR).At the quantity Q1,marginal revenue MR1 exceeds marginal cost MC1,so raising pr

15、oduction increases profit.At the quantity Q2,marginal cost MC2 is above marginal revenue MR2,so reducing production increases profit.The profit-maximizing quantity QMAX is found where the horizontal price line intersects the marginal-cost curve.14.2.2 The Marginal-Cost Curve and The Competitive Firm

16、s Supply CurveProfit maximization occurs at the quantity where marginal revenue equals marginal cost.When MR MC increase QWhen MR MC decrease QWhen MR=MC Profit is maximizedThe portion of marginal-cost curve that lies above average variable cost is the competitive firms short-run supply curve.A gene

17、ral rule for profit maximization:At the profit-maximizing level of output,marginal revenue and marginal cost are exactly equal.For any given price,the competitive firms profit-maximizing quantity of output is found by looking at the intersection of the price with the marginal-cost curve.In Figure 1,

18、that quantity of output is QMAX.In essence,because the firms marginal-cost curve determines the quantity of the good the firm is wiling to supply at any price,it is the competitive firms supply curve.Figure 2 Marginal Cost as the Competitive Firms Supply CurveCopyright 2004 South-WesternQuantity0Pri

19、ceMCATCAVCP1Q1P2Q2This section of thefirms MC curve isalso the firms supplycurve.An increase in the price from P1 to P2 leads to an increase in the firms profit-maximizing quantity from Q1 to Q2.because the marginal-cost curve shows the quantity supplied by the firm at any given price,it is the firm

20、s supply curve.Figure 14-2.Marginal Cost as the CompetitiveFirms Supply Curve PriceQuantity0Q1P1Q2MCATCAVCP2This section of the firms MC curve is also the films supply curve.14.2.3 The Firms Short-Run Decision to Shut DownA shutdown refers to a short-run decision not to produce anything during a spe

21、cific period of time because of current market conditions.Exit refers to a long-run decision to leave the market.14.2.3 The Firms Short-Run Decision to Shut DownThe firm considers its sunk costs when deciding to exit,but ignores them when deciding whether to shut down.Sunk costs are costs that have

22、already been committed and cannot be recovered.The firm shuts down if the revenue that it gets from producing is less than the variable cost of production.Shut down if TR VCShut down if TR/Q VC/QShut down if P AVC 14.2.3 The Firms Short-Run Decision to Shut DownFigure 3 The Competitive Firms Short R

23、un Supply CurveCopyright 2004 South-WesternMCQuantityATCAVC0CostsFirmshutsdown ifP AVC,firm will continue to produce in the short run.If P ATC,the firm will continue to produce at a profit.In the short run,the competitive firms supply curve is its marginal-cost curve(MC)above average variable cost(A

24、VC).If the price falls below average variable cost,the firm is better off shutting down.Figure14-3.The Competitive Firms Short-Run Supply Curve CostsQuantity0Firm shuts down if PATC,the firm will continue to produce at a profit.If PAVC,firm will continue to produce in the short run.Cost and Revenue,

25、(dollars)MCMR1AVCATCMARGINAL REVENUE-MARGINAL COST APPROACHQuantity SuppliedMR2MR3MR4MR5P1P2P3P4P5Q2Q3Q4Q5Marginal Cost&Short-Run SupplyDo notProduce Below AVCCost and Revenue,(dollars)MCMR1MARGINAL REVENUE-MARGINAL COST APPROACHQuantity SuppliedMR2MR3MR4MR5P1P2P3P4P5Q2Q3Q4Q5Marginal Cost&Short-Run

26、SupplyYields theShort-RunSupply CurveSupplyNoProductionBelow AVCMARGINAL REVENUE-MARGINAL COST APPROACHMarginal Cost&Short-Run SupplyAVC2MC2Higher Costs Move theSupply Curve to the LeftCost and Revenue,(dollars)MC1AVC1Quantity SuppliedS1S2MARGINAL REVENUE-MARGINAL COST APPROACHMarginal Cost&Short-Ru

27、n SupplyAVC2MC2Lower Costs Movethe Supply Curveto the RightCost and Revenue,(dollars)MC1AVC1Quantity SuppliedS1S2Sometime in your life you have probably been told,“Dont cry over spilt milk,”or“Let bygones be bygones.”These adages hold a deep truth about rational decision-making.Economists say that a

28、 cost is a sunk cost when it has already been committed and cannot be recovered.In a sense,a sunk cost is the opposite of an opportunity cost:An opportunity cost is what you have to give up if you choose to do one thing instead of another,whereas a sunk cost cannot be avoided,regardless of the choic

29、es you make.Because nothing can be done about sunk costs,you can ignore them when making decisions about various aspects of life,including business strategy.14.2.4 Spilt Milk and Other Sunk CostsOur analysis of the firms shutdown decision is one example of the irrelevance of sunk costs.We assume tha

30、t the firm cannot recover its fixed costs by temporarily stopping production.As a result,the firms fixed costs are sunk in the short run,and the firm can safely ignore these costs when deciding how much to produce.The firms short-run supply curve is the part of the marginal-cost curve that lies abov

31、e average variable cost,and the size of the fixed cost does not matter for this supply decision.14.2.4 Spilt Milk and Other Sunk CostsThe irrelevance of sunk costs is also important for personal decisions.Imagine,for instance,that you place a$10 value on seeing a newly released movie.You buy a ticke

32、t for$7,but before entering the theater,you lose the ticket.Should you buy another ticket?Or should you now go home and refuse to pay a total of$14 to see the movie?The answer is that you should buy another ticket.The benefit of seeing the movie($10)still exceeds the opportunity cost(the$7 for the s

33、econd ticket).The$7 you paid for the lost ticket is a sunk cost.14.2.4 Spilt Milk and Other Sunk CostsIn the long run,the firm exits the market if the revenue it would get from producing is less than the total costs.Exit if TR TCExit if TR/Q TC/QExit if P TCEnter if TR/Q TC/QEnter if P ATC 14.2.5 Th

34、e Firms Long-Run Decision to Exit or Enter a MarketFigure 4 The Competitive Firms Long-Run Supply CurveCopyright 2004 South-WesternMC=long-run SFirmexits ifP ATC In the long run,the competitive firms supply curve is its marginal-cost curve(MC)above average total cost(ATC).If the price falls below av

35、erage total cost,the firm is better off exiting the market.CostsQuantity0Firm exits if PATCFigure 4 The Competitive Firms Long-Run Supply Curve The competitive firms long-run supply curve is the portion of its marginal-cost curve that lies above average total cost.1.Short-Run Supply CurveThe portion

36、 of its marginal cost curve that lies above the minimum point of average variable cost.2.Long-Run Supply CurveThe portion of The marginal cost curve above the minimum point of its average total cost curve.The Supply Curve in a Competitive MarketCostsQuantity0MCATCFirms long-run supply curveFigure 14

37、-4.The Competitive Firms Long-Run Supply Curve Recall that profit equals total revenue(TR)minus total cost(TC):Profit=TR-TCProfit=(TR/Q-TC/Q)QProfit=(P-ATC)QNote that TR/Q is average revenue,which is the price P,and TC/Q is average total cost ATC.Therefore,14.2.6 Measuring Profit in our graph for th

38、e Competitive MarketFigure 5 Profit as the Area between Price and Average Total CostCopyright 2004 South-Western(a)A Firm with ProfitsQuantity0PriceP=AR=MRATCMCPATCQ(profit-maximizing quantity)ProfitFigure 5 Profit as the Area between Price and Average Total CostCopyright 2004 South-Western(b)A Firm

39、 with LossesQuantity0PriceATCMC(loss-minimizing quantity)P=AR=MRPATCQLossFigure 5 Profit as the Area between Price and Average Total Cost(a)A Firm with ProfitsPriceQuantity0ATCMCATCP=AR=MRPProfitQ(profit-maximizing quantity)(b)A Firm with LossesPriceQuantity0ATCMCATCP=AR=MRPLoss(profit-maximizing qu

40、antity)Q Figure 14-5.Profit as the Area between Price and Average Total Cost The area of the shaded box between price and average total cost represents the firms profit.The height of this box is price minus average total cost(P-ATC),and the width of the box is the quantity of output(Q).In panel(a),p

41、rice is above average total cost,so the firm has positive.in panel(b),price is less than average total cost,so the firm has losses.Market supply equals the sum of the quantities supplied by the individual firms in the market.14.3 The Supply Curve in a Competitive MarketFor any given price,each firm

42、supplies a quantity of output so that its marginal cost equals price.The market supply curve reflects the individual firms marginal cost curves.14.3.1 The Short Run:Market Supply with a Fixed Number of FirmsFigure 6 Market Supply with a Fixed Number of FirmsCopyright 2004 South-Western(a)Individual

43、Firm SupplyQuantity(firm)0PriceMC1.00100$2.00200(b)Market SupplyQuantity(market)0PriceSupply1.00100,000$2.00200,000When the number of firms in the market is fixed,the market supply curve,shown in panel(b),reflects the individual firms marginal-cost curves,shown in panel(a).Here,in a market of 1,000

44、firms,the quantity of output supplied to the market is 1,000 times the quantity supplied by each firm.PriceQuantity(firm)0$2.00MC(a)Individual Firm Supply2001001.00PriceQuantity(market)0$2.00Supply(b)Market Supply200,000100,0001.00Figure 14-6.Market Supply with a Fixed Number of FirmsQuestion:竞争市场的需

45、求曲线为竞争市场的需求曲线为Q=7000-2000P,假假设市场有设市场有1000个相同的厂商，每一个厂商的边际成本个相同的厂商，每一个厂商的边际成本MC=q+2,其中其中q为单个厂商的产量，试求市场供给为单个厂商的产量，试求市场供给曲线的表达式，均衡价格和均衡数量曲线的表达式，均衡价格和均衡数量.解：单个厂商的边际成本为 P=MC=q+2,即q=P-2.竞争市场的供给曲线应是1000个相同厂商的边际成本曲线的水平相加。即Q=1000q=1000P-2000.由于竞争市场的需求曲线为：Q=7000-2000P,求得：7000-2000P=1000P-2000,so 均衡价格P=3,均衡数量Q=

46、1000 P-2000=1000.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 the price.14.3.2 The Long Run:Market Supply with Entry and ExitFirms will enter or exit the market unti

47、l profit is driven to zero.Thus,in the long run,price equals the minimum of average total cost,as shown in panel(a).The number of firms adjusts to ensure that all demand is satisfied at this price.The long-run market supply curve is horizontal at this price,as shown in panel(b).Figure 14-7.Market Su

48、pply with Entry and Exit(a)Firms Zero-Profit ConditionPriceQuantity(firm)0ATCMCATCP=minimum(b)Market SupplyPriceQuantity(market)0SupplyAt 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 tota

49、l cost are driven to equality.Long-run equilibrium must have firms operating at their efficient scale.14.3.2 The Long Run:Market Supply with Entry and ExitTo understand the zero-profit condition more fully,recall that profit equals total revenue minus total cost,and that total cost includes all the

50、opportunity costs of the firm.In particular,total cost includes the opportunity cost of the time and money that the firm owners devote to the business.In the zero-profit equilibrium,the firms revenue compensates the owners for the time and money they expend to keep the business going.14.3.3 Why Do C