Economics is not concerned solely with the optimum allocation of resources, but with wider questions of equity and the distribution of costs and benefits among individuals, regions, etc. It is thus concerned with the question: who does what, to whom, and at whose expense? In a sense this concern complements the intertemporal considerations noted above. A dollar to one person is not necessarily worth the same amount to another. Since economics assumes that marginal values decline as income increases, interpersonal differences in income may thus affect any overall measure of consumer benefit.