Paths to Zero Population Growth

Fertility rates in the U.S. have been below the replacement level for nearly a decade so that in the absense of immigration the population would soon begin to decline. However during the same period there has been an excess in the number of immigrants and refugees over the number of emigrants. If the total fertility rate remains constant mortality rates stay constant and the volume of annual net immigration persists at the same level in each age-group the population will evolve to a stationary state. The size and age structure of such a stationary population will be independent of the current composition of the population but only on future fertility mortality and immigration. To illustrate this Table 1 shows the varying sizes of a stationary population that would result from differing levels of fertility and immigration. It is more difficult to estimate the length of time it would take before the U.S. would achieve a stationary population but is probably a longterm matter. Although many generations may pass before the U.S. population actually stabilizes tying numerical limits on immigration to contemporary fertility levels may have several shortterm advantages not the least of which is the flexibility such a policy would offer. Moreover estimates of the stationary population associated with various levels of immigration are important for understanding the eventual impact of immigration policies. If illegal immigration were eliminated and fertility remained at its present level with the 270000 annual immigrants (the number who may enter the U.S. for permanent residence under current law) and the absense of refugees the U.S. population would stabilize at about 150 million people. The Canadian and Australian governments are currently experimenting with flexible immigration policies to achieve desired levels of population growth.