【正文】 it Maximization and Competitive Supply 42 of 36 Copyright 169。 2022 Pearson Education, Inc. Publishing as Prentice Hall ? Microeconomics ? Pindyck/Rubinfeld, 7e. 廠商的長期均衡 Q P Q P D S’ AC MC（ S） S’’ S D P* 廠商的情況 市場(chǎng)的情況 D’ D’’ 長期均衡：邊際成本 =平均成本 =市場(chǎng)價(jià)格 Chapter 8: Profit Maximization and Competitive Supply 43 of 36 Copyright 169。 2022 Pearson Education, Inc. Publishing as Prentice Hall ? Microeconomics ? Pindyck/Rubinfeld, 7e. CHOOSING OUTPUT IN THE LONG RUN LongRun Competitive Equilibrium Entry and Exit In a market with entry and exit, a firm enters when it can earn a positive longrun profit and exits when it faces the prospect of a longrun loss. ● longrun petitive 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 equals quantity demanded. A longrun petitive equilibrium occurs when three conditions hold: 1. 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 the quantity supplied by the industry is equal to the quantity demanded by consumers. Chapter 8: Profit Maximization and Competitive Supply 44 of 36 Copyright 169。 2022 Pearson Education, Inc. Publishing as Prentice Hall ? Microeconomics ? Pindyck/Rubinfeld, 7e. CHOOSING OUTPUT IN THE LONG RUN LongRun Competitive Equilibrium Firms Having Identical Costs To see why all the conditions for longrun equilibrium must hold, assume that all firms have identical costs. Now 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. Firms Having Different Costs Now 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 opportunity cost to the firm that holds it. Chapter 8: Profit Maximization and Competitive Supply 45 of 36 Copyright 169。 2022 Pearson Education, Inc. Publishing as Prentice Hall ? Microeconomics ? Pindyck/Rubinfeld, 7e. CHOOSING OUTPUT IN THE LONG RUN LongRun Competitive Equilibrium The Opportunity Cost of Land 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 substantially increase the store’s accounting profit because the cost of the land is based on its historical cost. Economic Rent ● economic rent Amount that firms are willing to pay for an input less the minimum amount necessary to obtain it. Chapter 8: Profit Maximization and Competitive Supply 46 of 36 Copyright 169。 2022 Pearson Education, Inc. Publishing as Prentice Hall ? Microeconomics ? Pindyck/Rubinfeld, 7e. CHOOSING OUTPUT IN THE LONG RUN In the long run, in a petitive market, the producer surplus that a firm earns on the output that it sells consists of the economic rent that it enjoys from all its scarce inputs. Producer Surplus in the Long Run Chapter 8: Profit Maximization and Competitive Supply 47 of 36 Copyright 169。 2022 Pearson Education, Inc. Publishing as Prentice Hall ? Microeconomics ? Pindyck/Rubinfeld, 7e. CHOOSING OUTPUT IN THE LONG RUN Firms Earn Zero Profit in LongRun Equilibrium In longrun equilibrium, all firms earn zero economic profit. In (a), a baseball team in a moderatesized 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 plus the average economic rent is equal to the ticket price. When the opportunity cost associated with owning the franchise(專營權(quán) )is taken into account, the team earns zero economic profit. Figure Producer Surplus in the Long Run Chapter 8: Profit Maximization and Competitive Supply 48 of 36 Copyright 169。 2022 Pearson Education, Inc. Publishing as Prentice Hall ? Microeconomics ? Pindyck/Rubinfeld, 7e. THE INDUSTRY’S LONGRUN SUPPLY CURVE ConstantCost Industry ● constantcost industry Industry whose longrun supply curve is horizontal. LongRun Supply in a ConstantCost Industry In (b), the longrun supply curve in a constantcost industry is a horizontal line SL. When demand increases, initially causing a price rise (represented by a move from point A to point 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)). Figure The longrun supply curve for a constantcost industry is, therefore, a horizontal line at a price that is equal to the longrun minimum average cost of production. Chapter 8: Profit Maximization and Competitive Supply 49 of 36 Copyright 169。 2022 Pearson Education, Inc. Publishing as Prentice Hall ? Microeconomics ? Pindyck/Rubinfeld, 7e. THE INDUSTRY’S LONGRUN SUPPLY CURVE IncreasingCost Industry ● increasingcost indu