The major concern in this chapter is to sample and review literature of the past four decades relating to the significance of changes in age structure owing to population aging (Cowgill), especially with reference to their impact on dependency and the economic state of older dependents. However, the impact of these changes in age structure associated with decline in the rate of population growth must be distinguished analytically from the impact of decline in the rate of population growth as such (e.g., see Sauvy, 1948). The nature of the relationship between decline in the rate of population growth and increase in the relative number of older persons was illustrated broadly in Tables 2.1 and 2.2, and in greater detail in Table 2.6.

Population aging alters the age structure of the dependent population and therewith the means through which support is transferred to dependents from the individuals and institutions with whom this support originates. For example, given expectation of life at birth of 70.2 years and a Gross Reproduction Rate of 2, persons under 15 and over 59 in a stable population will constitute 45.3 percent of the population, with only 17.6 percent being 60 or more years of age. If, however, the Gross Reproduction Rate should settle in the neighborhood of the replacement level, about 40 percent of the population will be under 15 and over 59, and about one-half of these will be 60 or more years old (United Nations, 1956, p. 27; also United Nations, 1973). Should nondependent age in our example be defined as 18–64 instead of 15–59, a parallel change in the age structure of dependents would occur (e.g., see tables in Coale and Demeny).