Commentary: The changing relation between mortality and income.

cited in defence of his method: once several competing explanations have been shown to be impossible, then the improbable must be true. This is not an entirely satisfying sort of argument and would be considerably strengthened if evidence of a strong association between health care interventions and national levels of life expectancy could have been shown to be associated temporally. The second is that Professor Preston invoked a set of universally shared values to account for the diffusion of health-promoting technologies among countries. This is at best shorthand for what I think Professor Preston would agree is a far more complex phenomenon. The diffusion of innovations has been studied in great detail at the individual level of analysis, and much is known about it. 11 Less is understood about the diffusion process as it operates among institutions and countries. But surely he is correct that in the 19th century a variety of important innovations spread among European nations at very different levels of economic development. These included not only systems for the delivery of clean water and the disposal of sewage, 12,13 but legal changes having to do with quarantine 14 as well as with health insurance. 15 But the spread of these institutional and technological innovations involved political processes in the 19th century, as they do today and as my discussion of health policy was meant to suggest. That they also involve universally shared values is not so obvious. If they did, in the United States there would be a universal entitlement to health care. Despite this caveat, it should be clear that Professor Preston's article is a rich one. While it does not slight the importance of economic development for the improvement of the health of populations, it provides support for the importance of social interventions. Sadly, the policy implications have not been acted upon as thoroughly as one might have wished. References 1 Preston S. The changing relation between mortality and economic development. Understanding the relation between economic development and health is one of the most intriguing problems facing public health. Living standards and longevity have improved together, but the relation between them is not straight forward. Preston 1 provided us with the bare bones of the puzzle: there are very close cross-sectional relationships (correlation coefficients of between 0.8 and 0.9) between the log of national income per head and life expectancy at birth. Yet while this …