Many studies document failures of expected utility’s key assumption, the independence axiom. Here, we show that independence can be decomposed into two distinct axioms - betweenness and homotheticity - and that these two axioms are necessary and sufficient for independence. Thus, independence...

The most widely used economic models of social preferences are specified only for certain outcomes. There are two obvious methods of extending them to lotteries. If we do so by expected utility theory, so that the independence axiom is satisfied, our results imply that the resulting preferences...