1. Samuel H. Preston, Mortality Patterns in National Populations (Academic Press, 1976).
2. World Development Report, 1980 (World Bank, 1980). The low estimate assumes a life expectancy of sixty for China; the high would be in line with the Bank's assertion that it is currently seventy. Even if life expectancy in the People's Republic were lower than this, however, the world average could quite easily exceed sixty-three, for in many regions of the world estimates lag far behind the gains the people have achieved. A recent trip to Java, for example, has convinced me that Djakarta's mortality data understate the length of life on that island of ninety million by at least five years.
3. With life expectancy at eighteen for men and twenty for women, parents must have an average of six and a half or seven children to keep the population from declining. See Ansley J. Coale and Paul Demeny, Regional Model Life Tables and Stable Populations (Princeton University Press, 1966). Few societies have registered fertility rates much higher than this; when they have, it has seldom been under the harsh conditions such a low life span would imply. Archaeologists now tell us that Neolithic man's lifespan was about eighteen to twenty years, and we know that his life was a battle to maintain his numbers.
4. The rich and the poor are still separated by an enormous gap in life chances: infant mortality is four or five times higher today in the poor world than the rich, and a baby from the less developed regions can expect to die nearly twenty years before one who was fortunate enough to have been born at the same time in Europe, North America, Japan, Australia, New Zealand, or Israel. But if we take these tragic differences to mean that the poor have nothing to show for their participation in the twentieth century, we will be seriously mistaken. Progress in the less developed countries has been rapid and substantial. In India, for example, the length of the average life has nearly doubled since Independence. (Those who claim that the plight of the subcontinent's poor has gone unimproved for centuries always seem to forget this.) Over the past generation poor nations have consistently outpaced rich nations in the race to a healthier life. From 1960 to 1975, no rich country managed to improve its life expectancy by as much as 10 percent; by contrast, not a single poor country raised its own standing by less than 10 percent. These gains were absolute as well as relative. Since 1950 the collective life expectancy of the rich nations has increased by about a decade; for the poor nations, it is up more than fifteen years. See Health: A Sector Paper (World Bank, February 1980) and World Atlas of the Child (World Bank, 1979).
5. See Ansley J. Coale, Barbara A. Anderson, and Erna Harm, Human Fertility in Russia Since the Nineteenth Century (Princeton University Press, 1978) and V.O. Schmelz, Infant and Early Childhood Mortality among Jews of the Diaspora (Jerusalem, 1971).