As populations age and medical spending rises, there is no doubt that the medical system will account for an increasing part of economic activity. But how much more, and which countries will be most affected? Those are the questions I address in this paper. To answer them, I develop a model to forecast medical spending in OECD countries. The results yield several important conclusions, ranging from 2 to 4 percent of GDP in the next half century. Expected technological innovation in medicine raises the projected increase in the next 30 years to as high as 9 percent of GDP. Overall, the US and Japan will be among the most affected countries, with the UK being least affected. In Japan, the primary issue is demographic change, while medical cost increases are more important in the US.

Mortality rates in the US fell more rapidly during the late 19th and early 20th Centuries than any other period in American history. This decline coincided with an epidemiological transition and the disappearance of a mortality “penalty” associated with living in urban areas. There is little empirical evidence and much unresolved debate about what caused these improvements, however. This paper investigates the causal influence of clean water technologies – filtration and chlorination – on mortality in major cities during the early 20th Century. Plausibly exogenous variation in the timing and location of technology adoption is used to identify these effects, and the validity of this identifying assumption is examined in detail. We find that clean water was responsible for nearly half of the total mortality reduction in major cities, three-quarters of the infant mortality reduction, and nearly two-thirds of the child mortality reduction. Rough calculations suggest that the social rate of return to these technologies was greater than 23 to 1 with a cost per life-year saved by clean water of about $500 in 2003 dollars. Implications for developing countries are briefly considered.