IN THIS SUPPLEMENT, we provide several supporting results that are used in the main paper. In Section S.1, we provide a general local expected-utility result for mixture-averse preferences that nests Proposition 1 in the main paper as a special case. In Section S.2, we establish the relationship between mixture-averse preferences and several prominent non-expected-utility theories, including rank-dependent utility, betweenness, disappointment aversion, and cautious expected utility. Section S.3 describes the implications of preference for diversification for insurance demand, and discusses how preference for diversification is equivalent to risk aversion for either rank-dependent utility or any preference that is quasiconcave in probabilities. Section S.4 establishes the existence of a value function for the optimal risk attitude representation. Proofs are contained in Section S.5.