Admission of more than one million immigrants per year adds significantly to the rapid population growth of the United States. Because some immigrants leave voluntarily or are deported the net population increase each year from immigrants is a bit less than one million according to the U.S. Census Bureau (USCB). The USCB’s annually estimates the amount of population change from births, deaths, net domestic migration (interstate), and net international migration. The latter category is mostly the arrival and departure of foreigners.

Since mass immigration was unleashed by legislation in 1965, the share of the U.S. population increase due to immigration has grown rapidly. For example, the USCB data show net immigration accounting for 32 percent of the increase for the 1990-1999 period. For the most recent period (2010-2014), the share grew to 40.2 percent.

Those percentages, however, understate the impact of immigration on population increase. That is because the other factor in population increase – natural change, or births less deaths – does not distinguish between the births to immigrants and those to the U.S. born population. Births to the foreign-born population are higher than those to the native-born population partly because of the fact a larger share of the foreign-born population is in the child-bearing years and partly because of larger family size.

An estimate of the full impact of immigration – the immigrants themselves and their U.S.-born children — on U.S. population increase is much higher than the USCB percentages show, and it also is rising. For the 1990-1999 period, the immigrant-related share of population increase was 57.7 percent. The estimate based on the most recent period (2010-2014) is that immigration accounts for 76.9 percent of U.S. population increase. 

Another measure of the impact of immigration on the country is the share of the population that is foreign born. In 1960, that share was 5.4 percent. By 2000, the share had more than doubled to 11.1 percent, and as of 2014 the USCB estimates the share at 13.1 percent. The USCB issued an estimate in 2014 that if current trends continue the foreign-born share of the population will reach 18.7 percent by 2060. Of course, the current trend could be changed, because immigration admission limits could be changed.