ABSTRACT
In order to improve hazard management, a risk assessment industry has developed which combines the efforts of physical, biological, and social scientists in an attempt to identify hazards and measure the frequency and magnitude of their consequences. When lay people are asked to evaluate risks, they seldom have statistical evidence on hand. One heuristic that has special relevance for risk perception is known as "availability". In order to be of assistance in the hazard management process, a theory of perceived risk must explain people's extreme aversion to some hazards, their indifference to others, and the discrepancies between these reactions and experts' recommendations. Disagreements about risk should not be expected to evaporate in the presence of "evidence." Definitive evidence, particularly about rare hazards, is difficult to obtain. The very discussion of any low-probability hazard may increase the judged probability of that hazard regardless of what the evidence indicates.
