The Changing Relation between Mortality and level of Economic Development

Summary A very simple technique has been used to shed light on a number of questions about the influence of economic level on national mortality trends and differentials. Scatter-diagrams of the cross-sectional relation between national income per head and life expectancy are developed for three decades during the twentieth, century. The relations established appear to shift systematically during the century. In general, in order to attain a certain life expectancy between 40 and 60 a nation requires an income level almost three times greater in the 1930s than in the 1960s This shift is corroborated by a changing structure of mortality by cause of death for populations at equivalent mortality levels. The magnitude of the shifts, combined with regional income data suggests that some 75–90 per cent of the growth in life expectancy for the world as a whole over these three decades is attributable to factors exogenous to a nation's contemporary level of income Through similar techniques, improved nutrition and higher literacy can also be ruled out as important contributors. Nevertheless, the cross-sectional relation between income and life expectancy remains strong and there is some suggestion that mortality is now more responsive to variations in income levels among countries with national incomes below 400 (1963 dollars) than it was in the 1930s However, population size appears to respond so slowly to the mortality declines that typically result irom income growth that these mortality effects present little impediment to the process of economic development. Some of the variability in the cross-sectional mortality-income relation is doubtless due to variation in income distributions. Life expectancy in Venezuela, Mexico, and Colombia, countries with wide disparities in incomes, falls short of levels expected on the basis of their mean incomes. On the other hand, life expectancy in Soviet-bloc countries, where income equality is expected to be greater than average, also falls short of expected levels. Western and non-Western countries alike profited from the activity of ‘exogenous’ medical and public health factors. Differences between the two types of countries have been exaggerated by concentration on movements between equivalent mortality levels rather than during equivalent time periods. Recent work in historical demography suggests that the importance in Western mortality trends of endogenous factors consequent to rising standards of living has been overstated for earlier periods as well.