In the evaluation of public policies, a crucial distinction is between plans that involve purely idiosyncratic risk and those that generate correlated, or aggregate, risk. While natural, this distinction is not captured by standard utilitarian aggregators.
In this paper we revisit Harsanyi's (1955) celebrated theory of preferences aggregation and develop a parsimonious generalization of utilitarianism. The theory we propose captures sensitivity to aggregate risk in large populations and can be characterized by two simple axioms of preferences aggregation
