好不容易在cartoonbank找到了Mike Twohy的这幅漫画，就是想说明这个问题。
漫画主要描述的是，A man sits on a park bench reading the paper while a vender approaches with his stand, which has an umbrella on it. The man buys something from the vender. The man is back seated on the bench reading and the umbrella is now over him. The vender walks on. The umbrella on his stand is gone.
如果要追溯，我们可以先从亚当·斯密那个时代说起。在1977年，亚当·斯密是第一个在《国富论》（Wealth of Nations）中提到市场资源会被最有效率地使用的。亚当斯密的原文如下：...every individual necessarily labours to render the annual revenue of the society as great as he can. He generally, indeed, neither intends to promote the public interest, nor knows how much he is promoting it. By preferring the support of domestic to that of foreign industry, he intends only his own security; and by directing that industry in such a manner as its produce may be of the greatest value, he intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for the society that it was no part of it. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it. I have never known much good done by those who affected to trade for the public good.
我们同样可以在这幅漫画中感受到这只“看不见的手”（the Invisible Hand）。卖饮料的小贩同时拥有一把大伞。对于这两样东西，他心里自然有一个最低价（边际成本）。同样，公园里坐在长椅上看报纸的男士对饮料和阳伞也有一个可承受的最高价格（边际收益）。很显然，这位男士需要一把阳伞，阳伞的边际收益超过了它的价格，而饮料的价格超过了它的边际收益。他和小贩便进行了交易，于是产生了生产者剩余和消费者剩余。小贩卖出了阳伞，他的生产者剩余大于机会成本；男士购买了阳伞，获得了消费者剩余。在第三幅图中，两个人都比第一副图更有余裕(better off），阳伞被更有价值地利用了。这就是楼主所说的“交易增加福利”。
[此贴子已经被作者于2008-2-20 20:02:47编辑过]
发帖
雷达卡
加JingGuanBbs
京公网安备 11010802022788号
论坛法律顾问：王进律师
知识产权保护声明
免责及隐私声明
提升卡
置顶卡
沉默卡
变色卡
抢沙发
千斤顶
显身卡
