Moreover, what seem like obvious, commonsense policy solutions all too often have unintended consequences, because a policy’s targets are not passive objects, as in physics, but active agents who react in unpredictable ways. For example, price controls, rather than lowering prices, often cause scarcity and the emergence of a black market in which controlled commodities cost significantly more.
此外，似乎显而易见、堪称常识的政策解决方案往往会产生意料之外的效果，因为与物理学不同，政策的目标并不是被动的对象，而是主动的行为人，他们的反应难以预料。比如，价格管制而不是降低价格往往造成稀缺和黑市的产生，被管制商品在黑市上以高得多的价格出售。