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What Is "Conservatism"?

The most controversial aspect of this proposal within the full committee was its emphasis on "conservatism" as one—not the only—organizing principle to judge—not to prejudge—the merits of defaults and their alternatives. Supporters of this proposal are well aware that there are strengths and weaknesses of the conservative orientation that make it one of the most hotly-contested topics in all of environmental policy analysis, but also believe that few topics have been surrounded by as much confusion and misinformation. Some observers of risk assessment appear to be convinced that EPA and other agencies have so overemphasized the principle of conservatism as to make most risk estimates alarmingly false and meaningless; others, including at least one member of this committee, have instead suggested that if anything, the claims of these critics tend to be more reflexive, undocumented by evidence, and exaggerated than are EPA's risk estimates themselves (Finkel, 1989). It is clear that partisans cannot agree on either the descriptive matter of whether risk assessment is too conservative or on the normative matter of how much conservatism (perhaps any at all) would constitute an excess thereof. However, at least some of the intensity marking this debate is due to a variety of misimpressions about what conservatism is and what its ramifications are. Before laying out the proposal, therefore, some of these definitional matters will be discussed.

First, a useful definition of conservatism should help clarify it in the face of the disparate charges leveled against it. Conservatism is, foremost, one of several ways to generate risk estimates that allow risk management decisions to be made under conditions of uncertainty and variability. Simply put, a risk assessment policy that ignored or rejected conservatism would strive to always represent risks by their "true values" irrespective of uncertainty (or variability), whereas any attempt to consider adding (or removing) some measure of conservatism would lead the assessor to confront the uncertainty. Incorporating "conservatism" merely means that from out of the uncertainty and/or variability, the assessor would deliberately choose an estimate that he believes is more likely to overestimate than to underestimate the risk.

Rationality in managing risks (as in any endeavor of private or social decision making) involves the attempt to maximize the benefit derived from choice under specific conditions in the world. If we do not know those conditions (uncertainty) or do not know to whom these conditions apply (human interindividual variability), we have to make the choice that would be optimal for a particular set of conditions and essentially hope for the best. If the true risk we are trying to manage is larger or smaller than we think it is (or if there are individuals for whom this is so) then our choice may be flawed, but we still have to choose. Unlike the search for scientific truth, where the "correct" action in the face of uncertainty is to reserve one's judgment, in managing risks decisions are inevitable, since reserving judgment is exactly equivalent to making the judg-