 Within economics, the study of responsibility has emerged from the literature initiated by Duncan Foley [1967] and Hal Varian [1974] on fairness. An allocation is fair if and only if it is Pareto efficient and envy-free. An allocation is envy-free if no individual would prefer the outcome assigned to another individual to the outcome assigned to her. In an exchange economy, a competitive equilibrium that results from an initial, equal allocation of resources is both Pareto efficient and envy-free because each individual has the same set of options available to her. The competitive equilibrium is thus fair. 