The best current estimates suggest that the population ef the Third World is likely to triple in the next century and thereafter remain stable. Even if life expectancy were to rise at what appears to be the fastest rate possible, the effect on the ultimate, stable population of the Third World would be small. The reason is that the rate of population growth in the developing countries has become increasingly insensitive to changes in the death rate. The most important influences on growth are future trends in fertility and the large numbers of young people now reaching childbearing age, mainly as a result of high fertility in the recent past. If population growth is to be kept to a minimum, attention to reducing the birth rate will be most important. No substantial demographic consideration need stand in the way of the industrialized countries' carrying out their responsibility to help increase life expectancy in the developing countries....reductions in mortality have a diminishing influence on population growth as higher levels of life expectancy are achieved. The reduced effect is due to a shift in the age distribution of deaths. An infant saved from death from smallpox is enabled to live 50 or 60 years before dying of some other cause. A mother who would have died in childbirth gains another 30 or 40 years. A person 70 years old suffering from coronary insufficiency is granted another five years. As a result of such delays the average age at death and the proportion of deaths occurring among older people rise.
