La réconciliation des mesures des préférences sur la santé dans le certain et dans le risque

This paper studies the possibility of reconciling riskless and risky utility measures of health status by interpreting the latter using some assumptions of Kahneman and Tversky?s prospect theory: probability weighting and loss aversion. It also suggests that some biases in health states utility measures attributed to loss aversion may alternatively be explained by preference uncertainty. This assumption is based on the idea that when decisions are irreversible, i.e. when there is no possibility to go back to the statu quo after making a choice, preference uncertainty increases the relative cost of choosing. We thus propose to measure health state preferences in a context of certainty by using a new method that estimates ?Maximal Time of Treatment? (MTT). Unlike traditional preferences elicitation tools, the MTT method involves decisions that may be seen as reversible. As a consequence, the resulting measures should not be affected by biases arising from preference uncertainty. We test our assumptions in an empirical study, measuring the preferences of 235 persons over three hypothetical health states. The results confirm the identity between riskless utility as assessed by the MTT method and risky utility interpreted according to the axioms of prospect theory (using the corrective formulas developed by Bleichrodt, Pinto and Wakker [2001]). We conclude that MTT offers a promising way to avoid some biases in health state utility measures without having to quantify them.