Exponential Health Utility: A Characterization and Comments on a Paper by Happich and Mühlbacher.

In a recent paper Happich and Mühlbacher [Eur J Health Econom (2003) 4:292-294] proposed an axiom of constant absolute trade-off in life years, and studied the family of QALY models satisfying this axiom under expected utility and mutual utility independence between life years and health state. In this paper, we provide a complete characterization of the above-mentioned family of QALY models. This family should not be mistaken for the family of multiplicative expo-nential QALY models; in particular, it violates the zero-condition.