RISK ATTITUDE IN GAMBLES WITH YEARS OF LIFE - EMPIRICAL SUPPORT FOR PROSPECT-THEORY

According to prospect theory, risk altitude changes depending on wheth er a prospect is perceived as a gain or a loss relative to a reference or aspiration level. To investigate risk attitude with respect to yea rs of life, the authors elicited utilities at two occasions by the cer tainty equivalent method from 30 women from the general population. Th e respondents gave certainty equivalents to gambles with years of life . The gambles were two-outcome gambles with equal probabilities to exp erience each outcome. A shift from a risk-seeking towards a risk-avers e altitude was observed with increasing expected value ot the gambles. For each individual, the averaged responses over the two replications were fitted with an s-shaped logistic curve that showed an excellent fit (r2 greater-than-or-equal-to 0,97) for all respondents. The aspira tion level of survival can be derived from this function and was negat ively correlated with age (r = -0.43, p < 0.025). The data are consist ent with prospect theory and may explain why patients opt for risky tr eatments, since most of the respondents were risk-seeking in the short term.