今天读索维尔的Knowledge and Decisions，其中有段话颇有道理，翻译如下：

「 受到包含盈亏机制的价格体系的约束，经济决策很少将生产活动推进到“增加投入导致产出绝对减少”的地步。显然，为边际效益为负的投入物，支付真金白银毫无意义。然而，这并不意味着这种结果不会发生——当特定决策过程中的激励机制，使得个体决策者认为这样做合乎“理性”时，即便这一行为对“社会”（社会并不是一个具体的决策单位）有害，这类结果仍有可能出现。」

原文：Thomas Sowell：“Economic decision making within the constraints of a price system with profits and losses seldom leads to production in the region where more input leads to absolutely diminishing output. There is obviously no point spending hard cash for inputs whose incremental effect will be negative. However, this is not to say that such results do not happen, when the incentives in the particular decision-making process make it rational for the individual decision maker, however detrimental it may be to society, which is not a decision-making unit.”