Utilitarianism and Horizontal Equity

This paper establishes that, far from being able to derive the principle of horizontal equity from utilitarianism, the principle is actually in- consistent with utilitarianism in a variety of circumstances. We derive conditions under which (a) it is optimal to impose random tax schedules (ex post randomization) ; and (b) it is optimal to randomize the tax schedules imposed on a set of otherwise identical individuals (ex ante randomization). The implications for optimal tax theory are discussed. More generally, it is shown that there are a number of potentially important economic situations with which the principle of horizontal equity may be inconsistent not only with utilitarianism but even with Pareto optimality.