即高鸿业的微观也是这样的:
(2):
Given p, and the firm’s optimal output, s(p),the firm’s revenue can be represented in a graph of the supply curve by therectangle with height p and width s(p). The non-sunk cost of producing s(p) isthe area below the supply curve, so the producer’s surplus is the differencebetween these areas, which is the area above the supply curve and below p andbetween output 0 and output s(p). This is illustrated in the figure below.Producer’s surplus for price p* is the shaded region.
大家讨论一下。
我觉得第一种是错的,因为从y=0的y轴,到SMC和AVC的最低点相交,这之间的SMC,并不属于供给曲线。
不管利用微积分还是什么方法,如果要像第一张图那样,还要考虑SMC在供给曲线外的形状,那么难道表示供求曲线本身无法计算出生产者剩余吗?我觉得这是不正确的。
事实上,我在网上查资料的时候,发现国外在讲解生产者剩余时,也都是供求曲线来讲解,而不会将企业短期竞争的图来分析(我觉得是因为可能会混淆MC和供给曲线),比如曼昆的《经济学原理》。