第162页 Charpte 8 Analysis og Perfectly Competitive Markets

A. Suuply Behavior of the Competitive Firm
1. A perfectly competitive firm sells a homogeneous（同质的、类似的） product and is too small to affect the market price. Competitive firms are assumed to（被假定为） maximize their profits. To maximize profits, the competitive firm will choose that output level at which price equals the marginal cost of production,that is, P=MC Diagrammatically（图表地、概略地）, the competitive firm's equilibrium will come where the rising MC supply curve intersects its horizontal  demand curve.
2. Variable costs must be taken into consideration in determining a firm's short-run shutdown（关闭、停工、停业；使摆姿势） point. Below the shutdown point, the firm poses（引起、产生、造成；以--身份出现） more than its fixed costs. It will therefore produce nothing when price  falls below the shutdown price.
3.A competitives industry's long run supply curve, SlSl, must take into account the entry of new firms and the exodus （离去、退出）of old ones. In the long run, all of a firm's commmitments expire. It will stay in business only if price is at least as high as long-run average costs. These costs include out of pocket （赔钱、白花钱）payments to labor,lenders （贷方、出借人）,material suppliers, or landlords（房东、地主、店主） and opportunity costs, such as returns on the property assets owned by the firm.
A.竞争公司的供应行为
1.优秀的竞争企业会售卖类似的产品而且会由于本身的规模太小而影响到竞争价格。假设竞争企业为了获得最大的利润。为了（获得）最大的利润，竞争企业会以等于产品的边际成本的价格选择生产水平。也就是，P=MC。从图表中可以概略地看到，竞争企业会在上升的供应曲线MC与它的需求曲线相交处达到平衡。
2.可变成本在决定短期运行的拐点时必须加以考虑。在关闭点（拐点）以下，企业会产生更多的固定成本。因此当价格降到拐点以下时，企业就不会再生产了。
3.竞争公司长期运行的供应曲线，SISI，必须考虑新企业的进入和老企业的退出。长期运行中，长期运行中，所有企业的经营期限，只要价格达到长期运行的平均成本时，企业就会维持运营，这些成本包括花在劳动力、贷款、材料供应、土地租用以及机会成本，比如由企业拥有的财产权的回报。
B. Suuply Behavior in Competitive Industries
4.Each firm's rising MC curve is its supply curve. To obtain the supply curve of a group of competitive firms, we add horizontally their separate supply curves. The supply curve of the industry hence represents the marginal cost curve for the competitive industry as a whole.
5.Because firms can adjust production over time, we distinguish two different time periods:(a) short-run equilibrium, when avariable factors like labor can change but fixed factors like capital and number of firms cannot, and (b) long-run equilibrium, when the numbers of firms and plants, and all other conditions,adjust completely to the new demand conditions.
6. In the long-run, when firms are free to enter and leave the industry and no one firm has any particular advantage of skill or location, competition will eliminate （消除、排除、淘汰、除掉）any excess profits（超额利润） earned by existing firms in the industry. So, just as（正像、正如） free exit implies（暗示、说明、表明、意味、隐含） that price cannot fall below the zero-profit point, free entry implies that price cannot exceed long-run average cost in long-run equilibrium.
7. When an industry can expand its production without pushing up（推上去、增高） the prices of its factors of production, the resulting long-run supply curve will be horizontal. When an industry uses factors specific to it, such as scarce beachfront（海滩、湖边） property, its long-run supply curve will slope upward.
B.竞争行业的竞争行为
4.每家公司提升的边际成本曲线是它的供应曲线，为了获得整体的竞争企业的供应曲线，我们将他们单独的供应曲线水平相加。因此，行业的供应曲线代表了整体的竞争企业的边际成本曲线。
5.由因为企业能够随着时间而调节生产，所以我们要区分两个不同的时间段：
(a).短期运行平衡，像劳动力可变因素改变了而像资本和企业数量等固定因素无法改变时；
(b).长期运行平衡，当企业和工厂的数量，所有其他的情况，都彻底地改变到一个新的需求状态时。
6.长期运行中，当企业自由进入或离开行业时，没有哪个企业会有特别的技能和地点优势，竞争将消除由行业中的现存企业所赚取的超额利润。因此，正如自由退出意味着价格不能降到零利润点以下，自由进入意味着长期运行平衡中价格不能超过长期运营平均成本。
7.当一个行业为提高它的生产要素的价格时就能够扩大生产，长期运行的供应曲线的结果将是水平的；当一个行业使用了特殊的（生产）要素时，如稀缺的海边地产，它的长期运行的供应曲线将是缓慢上升的。
C.Special  Cases of Competitive Markets
8. Recall （回想、召回）the general rules that apply to（适用于、致力于） competitive supply and demand: Under the demand rule, an increase in the demand for a commodity (the supply curve being unchanged) will generally raise the price of the commodity and also increase the quantitiy demanded. A decrease in demand will have the opposite effects.
  Under the supply rule, an increase in the supply of a commodity (the demand curve being constant) will generally lower the price and increase the quantity sold. A decrease in supply has the opposite effects.
9.Important special cases include constant and increasing costs, completely inelastic（非弹性的） supply (which produces economic rents（租金、地租）), and backward-bending supply, These special cases will explain many important phenomena（现象） found in markets.</原文结束 >
C.竞争市场的特殊情况：
8.复习适用于竞争的供应和需求的普遍规律：在需求定律下，对一件商品的需求的增加（供应曲线不变的情况下）将总体提高（该）商品的价格，也会增加需求的数量。需求的减少将会出现相反的作用。
在供应定律下，对一件商品的供应量增加（需求曲线固定不变）将总体降低该商品的价格，也会增加销售的数量。供应的减少将会出现相反的作用。
9.重要的特殊情况包括成本固定不变和成本增加，完全地非弹性供应（产生经济的租金），反向弯曲的供应，这些特殊情况将解释许多市场中发现的重要现象。
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D. Efficiency and Equity（公平、公道、公平合理的事） of Competitive Markets
10.The analysis of competitive markets sheds（流出、流下、脱落、散布） light on（对--提供线索、对----透露情况、使---清楚地显出） the efficient （有效率的、生效的、能干的）organization of a society. Allocative efficiency （分配效率）occurs when there is no way of reorganizing production and distribution such that everyone's satisfaction can be improved. Put differently, an economy is efficient when no individual can be made better off without making another individual worse off.
11.Under ideal conditions, a competitive economy attains allocative efficiency. Efficiency requires that all firms are perfect competitors and that there are no extanalities（外部效应） like pollution or improved information. Efficiency implies that economic surplus equals consumer surplus plus producer surplus.
12.Efficiency comes because (a) when consumers maximize satisfaction, the marginal utility (in terms of （根据、就--而言、用---的话、以--为单位）leisure空闲时间) just equals the price; (b) when competitive producers supply goods , they choose output so that marginal cost just equals price; (c) since MU=P and MC=P, it follows that MU=MC, Thus the marginal social cost of producing a good under perfect competition just equals its marginal utility valuation（估价、定价、评价） in terms of goods or leisure forgone（没有也行、放弃）. It is exactly this condition- that the marginal gain to society from the last unit consumed equals the marginal cost to society of that last unit produced -- which guarantees that a competitive equilibrium is efficient.
13.There are exacting limits on the conditions under which an efficient competitive equlibrium can be attained: There can be no externalities and no imperfect competition, and consumers and producers must have complete information. The presence of imperfections leads to a breakdown（崩溃、倒塌、损坏、故障） of the price ration=marginal cost ratio=marginal utility ratio conditions, and hence to inefficiency.
14. The outcomes （结果、成果、出品）of competitive markets, even when efficient, may not be socially desirable. Competitive markets by themselves will not necessarily ensure outcomes that correspond（符合、一致） to the society's ideals about the fair distribution of income and consumption. Societies may modify（修改；改变、减轻、减缓） the laissez-faire（自由主义、放纵） equilbrium to change the income distribution to correct for a perceived（意识到、察觉、发觉、理解） unfairness of dollar votes of demand.
D.竞争市场的效率与公平
10.对竞争市场的分析可以清晰地显示出一个社会的组织情况，为了提高每个人的满意程度，没有办法进行再生产和再分配时就出现了分配效率，进行不同的尝试，当既不能使个体情况更好也不能使另外的个体间情况变得更糟时，经济就是有效的。
11.理想状态下，竞争经济获得分配效率。（该）效率要求所有企业都是完全竞争者，并且没有像污染和先进的信息等外部效应。效率表明经济余量等于消费余量加上产品余量。
12.效率的产生原因：
(a).当消费者获得最大满意度时，边际效用（就空闲时间而言）刚好等于价格；
(b).当竞争的生产者供应商品时，他们选择的（生产）输出是边际成本刚好等于价格；
(c).既然MU=P,而且MC=P，就可以得出MU=MC,因此，就商品和放弃的空闲时间而言，在完全竞争状态下生产一件商品的社会边际成本刚好等于它的社会边际效用估值。确切地说，这种情况下，消费的最后一个单位的社会边际所得等于生产最后一个单位的社会边际成本----这证明竞争平衡是有效的。
13.在有效竞争平衡可以获得的情况下，许多情况都会有明确的限制：没有外部效应而且没有不完全竞争，消费者和生产者必须都获得完整的信息，不完全竞争的现状将导致价格比率=边际成本比率=边际效用比率的情况彻底崩溃，因此是无效的。
14.竞争市场的结果，即使是在有效的时候，也许不是社会所渴望的，由他们自己创立的竞争市场就收入和消费分配来说，也不必确保达到符合社会理想状态的结果；社会也许会通过改变收入分配来矫正他们已察觉的收入不公的（情况），来减改变自由竞争状态的平衡。