Introduction (cont.)

Properties of stable populations (cont.)

It is possible to construct stable populations that are subject to constant age-specific migration rates, but unchanging migration rates are rarely encountered in practice, generally being more volatile than fertility and mortality, and there are few applications of stable population theory to open populations. In this session we will assume that stable populations are closed to migration.

Growth which is constant over time and proportional to the size of the population at any instant of time is called exponential growth, and has well defined mathematical properties. Stable populations have exponential growth rates, but the mathematical proof of this is beyond the scope of this course. We will accept the exponential nature of the growth, and starting from this premise, show what this implies for the relationship between fertility, mortality and age structure.