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1、第22章 厂商供给（Firm Supply） 完全竞争市场环境下的厂商供给,How does a firm decide how much product to supply? This mainly depends upon the firms technology market environment goals competitors behaviors,一、市场环境或市场结构 Market Environments,Are there many other firms, or just a few? Do other firms decisions affect our firms p
2、ayoffs? Is trading anonymous, in a market? Or are trades arranged with separate buyers by middlemen?,在经济分析中，根据不同的市场结构的特征，将市场划分为完全竞争市场、垄断垄断竞争市场、寡头市场和垄断市场四种类型。,市 场 类 型 的 划 分 和 特 征,Market Environments,Monopoly: Just one seller that determines the quantity supplied and the market-clearing price. Oligopo
3、ly: A few firms, the decisions of each influencing the payoffs of the others.,Market Environments,Monopolistic Competition: Many firms each making a slightly different product. Each firms output level is small relative to the total. Pure Competition: Many firms, all making the same product. Each fir
4、ms output level is small relative to the total.,不同市场结构下厂商决策的共性:,利润最大化 边际收益=边际成本，是确定厂商利润最大化的原则 在利润最大化产量为既定前提下，如果商品价格小于平均变动成本（短期）或者商品价格小于平均成本（长期），则厂商停止生产。,利润（Q）TR（Q）TC（Q） d（Q）/dQ0时，（Q）取得极值 即dTR（Q）/dQdTC（Q）/dQ0 即MRMC0 即MRMC,Market Environments,Later chapters examine monopoly, oligopoly. This chapter ex
5、plores only pure competition.,二、完全竞争厂商面临的需求曲线,If the firm sets its own price above the market price then the quantity demanded from the firm is zero. If the firm sets its own price below the market price then the quantity demanded from the firm is the entire market quantity-demanded.,Pure Competitio
6、n,So what is the demand curve faced by the individual firm?,Pure Competition,Y,$/output unit,Market Supply,Market Demand,pe,Pure Competition,y,$/output unit,Market Supply,pe,p,At a price of p, zero is demanded from the firm.,Market Demand,Pure Competition,y,$/output unit,Market Supply,pe,p,p”,At a p
7、rice of p” the firm faces the entire market demand.,At a price of p, zero is demanded from the firm.,Market Demand,Pure Competition,So the demand curve faced by the individual firm is .,Pure Competition,y,$/output unit,Market Supply,pe,p,p”,At a price of p” the firm faces the entire market demand.,A
8、t a price of p, zero is demanded from the firm.,Market Demand,Pure Competition,Y,$/output unit,pe,p,p”,Market Demand,Smallness,What does it mean to say that an individual firm is “small relative to the industry”?,Smallness,$/output unit,y,Firms MC,The individual firms technology causes it always to
9、supply only a small part of the total quantity demanded at the market price.,Firms demand curve,pe,y1,通常完全竞争厂商面临的需求曲线，简单起见，我们也可以用一条水平线表示，它同时表明完全竞争厂商是市场价格的接受者。,P,q（万）,P,S,D,0,0,Q（亿）,完全竞争厂商面临的需求曲线的移动 当其他因素，如经济中消费者收入水平的普遍提高，经济中先进技术的推广或政府有关政策的作用，使得众多的消费者的需求量与众多的生产者的供给量发生变化使市场均衡价格变化厂商的需求曲线的移动。,P,q（万）,Q（亿
10、）,P,0,0,P2,P1,S1,S2,D1,D2,d2,d1,三、厂商的短期供给决策 The Firms Short-Run Supply Decision,Each firm is a profit-maximizer and in a short-run. Q: How does each firm choose its output level?,The Firms Short-Run Supply Decision,Each firm is a profit-maximizer and in a short-run. Q: How does each firm choose its
11、output level? A: By solving,The Firms Short-Run Supply Decision,What can the solution ys* look like? 通常ys* 0:,P(y),y,ys*,For the interior case of ys* 0, the first- order maximum profit condition is,That is,So at a profit maximum with ys* 0, the market price p equals the marginal cost of production a
12、t y = ys*.,For the interior case of ys* 0, the second- order maximum profit condition is,That is,So at a profit maximum with ys* 0, the firms MC curve must be upward-sloping.,The Firms Short-Run Supply Decision,$/output unit,y,pe,ys*,y,MCs(y),$/output unit,y,pe,ys*,y,At y = ys*, p = MC and MC slopes
13、 upwards. y = ys* is profit-maximizing.,MCs(y),$/output unit,y,pe,ys*,y,At y = ys*, p = MC and MC slopes upwards. y = ys* is profit-maximizing.,At y = y, p = MC and MC slopes downwards. y = y is profit-minimizing.,MCs(y),The Firms Short-Run Supply Decision,$/output unit,y,pe,y,At y = ys*, p = MC and
14、 MC slopes upwards. y = ys* is profit-maximizing. So a profit-max. supply level can lie only on the upwards sloping part of the firms MC curve.,MCs(y),ys*,The Firms Short-Run Supply Decision,But not every point on the upward-sloping part of the firms MC curve represents a profit-maximum. 必须大于平均可变成本的
15、部分,The Firms Short-Run Supply Decision,But not every point on the upward-sloping part of the firms MC curve represents a profit-maximum. The firms profit function is If the firm chooses y = 0 then its profit is,The Firms Short-Run Supply Decision,So the firm will choose an output level y 0 only if,The Firms Short-Run Supply Decision,So the firm will choose an output level y 0 only if I.e., only if Equivalently, only if,The Firms Short-Run Supply Decision,AVCs(y),ACs(y),MCs(y),$/output unit,y,The Firms Short-Run Supply
