Egalitarian Collective Decision Making under Qualitative Possibilistic Uncertainty: Principles and Characterization

This paper raises the question of collective decisionmaking under possibilistic uncertainty; We study fouregalitarian decision rules and show that in the contextof a possibilistic representation of uncertainty, the useof an egalitarian collective utility function allows toget rid of the Timing Effect. Making a step further,we prove that if both the agents’ preferences and thecollective ranking of the decisions satisfy Dubois andPrade’s axioms (1995), and particularly risk aversion,and Pareto Unanimity, then the egalitarian collectiveaggregation is compulsory. This result can be seen asan ordinal counterpart of Harsanyi’s theorem (1955).