Attempts to Establish a Risk by Analogy

In this paper, we argue that risk in a new situation can be calculated by comparison with the most closely analogous previous situation that we can find. In many cases, such as automobile accidents, we argue that this year is analogous to preceding years. With toxic chemicals the analogy is less direct—we compare with other toxic chemicals or with chemicals shown to be toxic in other species. Because the unreliability or uncertainty of the analogy can be high, it is necessary to use less sensitive, but more reliable, methods of estimating risk to prevent continued use of a hazardous material, and subsequent tragedy if the hazard should turn out to be unexpectedly large. This suggests more robust techniques to reduce the regret, or societal cost of being wrong, because increased sensitivity is sometimes attained at the expense of sampling error.