Universal Social Ordering

We propose the concept of a universal social ordering, defined on the set of pairs of an allocation and a preference profile of any finite population. It is meant to unify evaluations and comparisons of social states with populations of possibly different sizes with various characteristics. The universal social ordering not only evaluates policy options for a given population but also compares social welfare across populations, as in international or intertemporal comparisons of living standards. It also makes it possible to evaluate policy options which affect the size of the population or the preferences of its members. We study how to extend the theory of social choice in order to select such orderings on a rigorous axiomatic basis. Key ingredients in this analysis are attitudes with respect to population size and the bases of interpersonal comparisons.