Ex Post Average Utilitarianism Can Be Worse for All Affected, Even If No Contingently Existing Person Is Affected

According to ex post average utilitarianism, prospect x is at least as good as prospect y if and only if the expected average well-being is at least as great in x as in y. Relative to the ex ante approach of taking the average of people’s expectations, this ex post approach has the advantage of not needing well-defined expectations of well-being for contingent people—people who exist in some but not all states of nature. Nevertheless, we show that ex post average utilitarianism can oppose the interests of all affected people. Moreover, we show this without relying on any comparisons of expectations of well-being for contingent people: our objection can be made with cases in which no contingently existing person is affected. Finally, we show that our objection can be made even if lifetime well-being has only an ordinal structure (in which case prior objections to average utilitarianism would not apply).