Arrovian Aggregation in Economic Environments: How Much Should We Know About Indifference Surfaces?

Arrow's celebrated theorem of social choice shows that the aggregation of individual preferences into a social ordering cannot make the ranking of any pair of alternatives depend only on individual preferences over that pair, unless the fundamental weak Pareto and nondictatorship principles are violated. In the standard model of division of commodities, we investigate how much information about indifference hypersurfaces is needed to construct social ordering functions satisfying the weak Pareto principle and anonymity. We show that local information such as marginal rates of substitution or the shapes "within the Edgeworth box" is not enough, and knowledge of substantially non-local information is necessary.