The consumer's perceptions of risk are a major consideration in the pre-purchase stage of the purchasing decision. Perceived risk is defined as "the consumer's perceptions of the uncertainty and adverse consequences of engaging in an activity". Risk consists of two dimensions: "consequences" - the degree of importance or the severity of an outcome and "uncertainty" - the consumer's subjective assessment of the likelihood of occurrence. For example, many tourists are fearful of air travel because, although the probability of being involved in an airline accident is very low, the consequences are potentially dire.