Assessing Risky Social Situations

This paper analyzes social situations in the context of risk. A new argument is proposed in order to defend the ex-post approach against Diamond’s (1967) famous critique of Harsanyi’s (1955) utilitarian theorem. It leads to a characterization of the criterion consisting in computing the expected value of the “equal-equivalent”. Characterizations of the ex-post maximin and leximin criteria, as well as a variant of Harsanyi’s theorem, are also obtained. It is examined how to take account of concerns for ex-ante fairness within this ex-post approach. Related issues are also addressed, such as the rescue problem or preference for catastrophe avoidance.