Fertility below replacement, stationary population through migration and effects of age structures

Abstract

Due to its declining fertility rate, Brazil is closer to the demographic conditions that determine population zero or negative growth, on the long run. However, there are no reasonable grounds to assert that the fertility rate will stabilize at replacement level or just below it. There are indications that it will be likely to descend to very low levels in coming decades. Theoretically, a stable and closed population with fertility rates below replacement level can return to zero growth if the population is subjected to changes in the constant annual number of entries derived from the return of fertility to replacement level. This may also occur due to constant positive net migration with constant and fixed age structure. Therefore, for a given set of rates of exits, there are an infinite number of equivalent stationary populations. Given fertility below replacement level, the present study uses Schmertmann’s theoretical model (1992) to simulate and examine, by comparison, (1) the age structure of the population of the State of São Paulo, Brazil, that has resulted from a rise in fertility to replacement level and (2) the age structures of this population, as made stationary through migration, assuming different scenarios of fertility and the age structure of immigrants.