Paul Samuelson made a series of important contributions to population theory for humans and other species, evolutionary theory, and the theory of age structured life cycles in economic equilibrium and growth. The work is highly abstract but much of it was intended to illuminate issues of...

Utilitarianism is the most prominent family of social welfare functions. We present three new axiomatic characterizations of utilitarian (that is, additively separable) social welfare functions in a setting where there is risk over both population size and the welfares of individuals. First, we...

The expectation of a sum of utilities is a core criterion for evaluating policies and social welfare under variable population and social risk. Our contribution is to show that a previously unrecognized combination of weak assumptions yields general versions of this criterion, both in...