Should we beware of the Precautionary Principle?
探讨预防原则是否与“三思而后行”的直觉相矛盾，并指出在科学不确定性下，延迟预防措施可能增加脆弱性，但早期行动具有期权价值，同时学习效应和风险溢价也会影响决策。
How should society deal with risks when there is scientific uncertainty about the size of these risks? There has been much recent discussion of the Precautionary Principle, which states that lack of full scientific knowledge should not be used as a reason to postpone cost-effective preventive measures. We show in this paper that the Precautionary Principle contradicts one important intuition about the right way to act in the face of risk, namely the principle of 'looking before you leap'. When we expect to learn more about the future, the effectiveness of our preventive measures will be greater if we learn before we act. However, a number of other ways of taking uncertainty into account are consistent with a reasonable interpretation of the Precautionary Principle. First, postponing preventive measures may increase our vulnerability to damage, which induces a precautionary motive for risk-prevention, similar to the precautionary savings motive. Secondly, stronger preventive actions often yield more flexibility for the future, so that acting early has an option value. Thirdly, when better information comes from a process of learning-by-doing, the risk associated with early events is amplified by the information they yield about the future. This plays a role analogous to that of an increase in risk aversion, making us more cautious. Fourthly, because imperfect knowledge of the risk makes it difficult to insure, the social cost of risk should include a risk premium. Finally, uncertainty about the economic environment enjoyed by future generations should be taken into account. This raises the benefit of acting early to prevent long-term risks. Copyright CEPR, CES, MSH, 2001.