Marginal Revenue $6.00 $6.00 $6.00 $6.00 $6.00 $6.00 $6.00 $6.00
Marginal Cost $2.00 $3.00 $4.00 $5.00 $6.00 $7.00 $8.00 $9.00
14.2.2 边际成本曲线和企业的供给曲线 The Marginal-cost Curve and the Firm’s S-Curve
Costs and Revenue The firm maximizes profit by producing the quantity at which marginal cost equals marginal revenue.
MC
ATC P=MR1 MC1 P = AR = MR AVC
0
Q1
当一个竞争企业使自己的销售量翻一番时， 它的产品价格和总收益会发生什么变动？
14.2 利润最大化与竞争企业的供给曲线 Profit Maximization And the Competitive Firm’s Supply Curve
竞争企业的目标是利润最大化，利润等于总收 益减总成本。我们刚刚讨论了企业的收益，而 且，在上一章中我们讨论了企业的成本。现在 我们就准备考察企业如何使利润最大化，通过 这种决策从而得出它的供给曲线。
Shut down if TR/Q < VC/Q
Shut down if P < AVC
The Firm’s Short-Run Decision torun supply curve. If P > ATC, keep producing at a profit. If P > AVC, keep producing in the short run.
14.2.1一个简单的利润最大化例子 A Simple Example of Profit Maximization
Price Quantiy Total Total Cost Profit (P) (Q) Revenue (TC) (TR-TC) 0 $0.00 $3.00 -$3.00 $6.00 1 $6.00 $5.00 $1.00 $6.00 2 $12.00 $8.00 $4.00 $6.00 3 $18.00 $12.00 $6.00 $6.00 4 $24.00 $17.00 $7.00 $6.00 5 $30.00 $23.00 $7.00 $6.00 6 $36.00 $30.00 $6.00 $6.00 7 $42.00 $38.00 $4.00 $6.00 8 $48.00 $47.00 $1.00
The Firm’s Short-Run Decision to Shut Down
The firm shuts down if the revenue it gets from producing is less than the variable cost of production.
Shut down if TR < VC
MC
ATC AVC
If P < AVC, shut down. 0 Quantity
小结：

停业原则：企业在收入刚好抵补它的可变成本或者损失正 好等于固定成本时，停业点就会出现。当价格低于该水平， 致使收入无法抵补它的可变成本时，企业就会停止生产, 以使其利润最大化（即损失最小化）。

关于企业停业点的分析得出了一个出人意料的结论：即使 追求利润最大化的企业亏损，它也可能在短期内继续经营。 尤其是对那些大量负债，从而拥有较高的固定成本的企业 （航空公司就是很好的例子）。
市场上有许多买者和许多卖者
各个卖者提供的物品大体上是相同的
企业可以自由地进入或退出市场
14.1.2 竞争企业的收益 The Revenue Of A Competitive Firm
竞争市场上的企业与经济中大 多数其他企业一样，努力使利 润最大化，利润等于总收益减 总成本。为了说明如何做到这 一点，我们首先考虑竞争企业 的收益。为了使事情具体化， 我们考虑一个特定企业：斯密 的家庭奶牛场。
QMAX
Quantity
Profit Maximization for the Competitive Firm
Profit maximization occurs at the quantity where marginal revenue equals marginal cost.
Profit Maximization for the Competitive Firm
14.1.2 竞争企业的收益 The Revenue Of A Competitive Firm

Total revenue for a firm is the selling price times the quantity sold. Average revenue tells us how much revenue a firm receives for the typical unit sold. In perfect competition, average revenue equals the price of the good. Marginal revenue is the change in total revenue from an additional unit sold. MR =TR/ Q. For competitive firms, marginal revenue equals the price of the good.
第十四章 竞争市场上的企业
Chapter 14
Firms in Competitive Markets
在本章中，你将

了解使一个市场具有竞争性的特点是什么


考察竞争企业如何决定生产多少产量
考察竞争企业如何决定什么时候暂时停产 考察竞争企业如何决定进入还是退出一个市场 说明企业行为如何决定市场短期与长期供给曲线


Total, Average, and Marginal Revenue for a Competitive Firm
Quantity (Q) 1 2 3 4 5 6 7 8 Price (P) $6.00 $6.00 $6.00 $6.00 $6.00 $6.00 $6.00 $6.00 Total Revenue Average Revenue Marginal Revenue (TR=PxQ) (AR=TR/Q) (MR=TR/ Q ) $6.00 $6.00 $12.00 $6.00 $6.00 $18.00 $6.00 $6.00 $24.00 $6.00 $6.00 $30.00 $6.00 $6.00 $36.00 $6.00 $6.00 $42.00 $6.00 $6.00 $48.00 $6.00 $6.00
停止营业指在某个特殊时期由于当前的市场条件而不生产任 何东西的短期决策，企业的退出是指离开市场的长期决策。 长期与短期决策不同，是因为大多数企业在短期中不能避开 它们的固定成本，而在长期中可以避开。这就是说，暂时停 止营业的企业仍然必须支付固定成本，而退出的企业既可以 节省固定成本，又可以节省可变成本。 现在我们来考虑什么决定企业的停止营业决策。如果企业停 止营业，它就失去了出售自己产品的全部收益。同时，它节 省了生产其产品的可变成本。因此，如果生产能得到的收益 小于生产的可变成本，企业就停止营业。

资料来源：

张淑云《经济学——从理论到实践》，化学工业出版社，2004 年。

对应知识点：“固定成本与可变成本”、“长期和短期”
14.2.4 覆水难收与沉没成本 Spilt Milk and Other Sunk Costs
This section of the firm’s MC curve is also the firm’s supply curve.
MC
P2
P1 ATC AVC
0
Q1
Q2
Quantity
14.2.3 企业的短期停止营业决策 The Firm’s Short-run Decision to Shut Down



Prologue
In this chapter we examine the behavior of competitive firms, such as your local gas station. You may recall that a market is competitive if each buyer and seller is small compared to the size of the market and, therefore, has little ability to influence market prices. By contrast, if a firm can influence the market price of the good it sells, it is said to have market power. Our analysis of competitive firms in this chapter will shed light on the decisions that lie behind the supply curve in a competitive market. Not surprisingly, we will find that a market supply curve is tightly linked to firms’ costs of production. (Indeed, this general insight should be familiar to you from our analysis in Chapter 7.) But among a firm’s various costs—fixed, variable, average, and marginal—which ones are most relevant for its decision about the quantity to supply? We will see that all these measures of cost play important and interrelated roles.