Health care extends life. Over the past half century, Americans spent a rising share of total economic resources on health and enjoyed substantially longer lives as a result. Debate on health policy often focuses on limiting the growth of health spending. We investigate an issue central to this debate: Is the growth of health spending the rational response to changing economic conditions - notably the growth of income per person? We develop a model based on standard economic assumptions and argue that this is indeed the case. Standard preferences - of the kind used widely in economics to study consumption, asset pricing, and labor supply - imply that health spending is a superior good with an income elasticity well above one. As people get richer and consumption rises, the marginal utility of consumption falls rapidly. Spending on health to extend life allows individuals to purchase additional periods of utility. The marginal utility of life extension does not decline. As a result, the optimal composition of total spending shifts toward health, and the health share grows along with income. This effect exists despite sharp diminishing returns in the technology of life extension. In projections based on the quantitative analysis of our model, the optimal health share of spending seems likely to exceed 30 percent by the middle of the century.
