This paper sketches a theory of the secular decline in morbidity and mortality that takes account of changes in human physiology since 1700. The synergism between technological and physiological improvements has produced a form of human evolution, much more rapid than natural selection, which is still ongoing in both OECD and developing countries.Thermodynamic and physiological aspects of economic growth are defined and their impact on growth rates is assessed. Implications of this theory for population forecasting, measurement of national income, demand for leisure, pension policies, and for the demand for health care are considered.
2The plunge in mortality rates during the early decades of the twentieth century delivered a major blow to the Maithusian theory of population. Improvements in mortality were supposed to be short lived because, under the conditions of population pressure against the food supply that Maithus specified, the elimination of deaths due to one disease would be replaced by those due to some other malady. Efforts to reconcile Maithusian doctrine with the observed mortality decline, to modify it, or to replace it produced a large new literature.
Explaining the Secular Decline in MortalityThe drive to explain the secular decline in mortality pushed research in three directions.First, there was a concerted effort to develop time series of death rates that extended as far back in time as possible in order to determine just when the decline in mortality began. Second, the available data on mortality rates were analyzed in order to identify factors that might explain the decline as well as to establish patterns or "laws" that would allow predictions of the future course of mortality.Third, a widespread effort was undertaken to determine the relationship between the food supply and mortality rates. There were several aspects to this effort. Perhaps the most important was the emergence of a science of nutrition that identified a series of diseases related to specific nutritional deficiencies and discovered the synergy between nutrition and infection (Scrimshaw, Taylor and Gordon 1968). Another aspect was the emergence of the field of development economics after World War II as part of the campaign to close the yawning gap in income, health, and life expectancy between the industrialized nations and the "developing nations." Still another aspect was the combined effort of economic and demographic historians to study the role of mortality crises and their relationship to famines during the seventeenth and eighteenth centuries.Prior to the 1960s, efforts to reconstruct the secular trend in European mortality were focused primarily on notable local communities and parishes. However, developments in about half a century earlier in France and its rate of decline during the first wave was more rapid.Perhaps the most surprising aspect of Figure 1 is the implication that the elimination of crisis mortality, whether related to famines or not, accounted for less than 10 percent of the secular declin...