To cite this version:Alain Chateauneuf, Michèle Cohen, Isaac Meilijson. More pessimism than greediness: a characterization of monotone risk aversion in the Rank-Dependent Expected Utility model. Economic Theory, Springer Verlag, 2005, 25, pp.649-667. 10.1007 More pessimism than greediness: a characterization of monotone risk aversion in the Rank-Dependent Expected Utility model Summary. This paper studies monotone risk aversion, the aversion to monotone, meanpreserving increase in risk (Quiggin [21]), in the Rank Dependent Expected Utility (RDEU) model. This model replaces expected utility by another functional, characterized by two functions, a utility function u in conjunction with a probability-perception function f . Monotone mean-preserving increases in risk are closely related to the notion of comparative dispersion introduced by Bickel & Lehmann [3,4] in Non-parametric Statistics. We present a characterization of the pairs (u; f ) of monotone risk averse decision makers, based on an index of greediness G u of the utility function u and an index of pessimism P f of the probability perception function f : the decision maker is monotone risk averse if and only if P f¸Gu . The index of greediness (non-concavity) of u is the supremum of u 0 (x)=u 0 (y) taken over y · x. The index of pessimism of f is the in¯mum ofv taken over 0 < v < 1. Thus, G u¸1 , with G u = 1 i® u is concave. If P f¸Gu then P f¸1 , i.e., f is majorized by the identity function. Since P f = 1 for Expected Utility maximizers, P f¸Gu forces u to be concave in this case; thus, the characterization of risk aversion as P f¸Gu is a direct generalization from EU to RDEU. A novel element is that concavity of u is not necessary. In fact, u must be concave only if P f = 1.