The U.S.-born children of resident aliens acquire U.S. citizenship at birth, so their birth is not included in U.S. Census Bureau (CB) data as part of the change in the immigrant population. But those immigrant births very much impact the rate of population change. An estimate can be made of the extent to which the disproportionately large number of immigrant births affect the overall population change when added to the change from net immigration.
A key factor in assessing the overall share of population increase is the estimate that births to the foreign-born population in 2010 amounted to 25 percent of all births, and, at that time, the foreign-born population was 12.9 percent of the U.S. population. Thus the foreign-born population's share of births was about double its size. Researchers at the Pew Hispanic Center provided similar but different numbers. They put the number of U.S. births by the foreign-born population at 23 percent and the share of foreign-born women in their child-bearing years (15-44) at 17 percent - again about twice their share. We, therefore, use CB estimates of immigrant population size and add to it an estimated amount of births to immigrants - based on multiplying twice the foreign-born share of the population times the annual average number of births. We reduce the number of births to the U.S.-born population by that same number of estimated births to the immigrant population.There is also an adjustment for the CB data on deaths to reflect the smaller share of deaths attributable to the immigrant population. This lower rate is a factor of the generally smaller share of immigrants in the older age brackets. We used a factor of one-half the size of the foreign-born population, i.e. the inverse of the birth adjustment.
The U.S. Census Bureau annually (except for Decennial Census years) estimates the amount of population change from Net International Migration (NIM) in the Current Population Survey (CPS). Those data account for new residents arriving from abroad and U.S. residents leaving to reside abroad. For the most part, this is immigrants arriving and leaving. Because the the most recent CPS data cover a shorter period than for the previous decades, we convert the data to an annual average.
In December, 2014, the CB released a new U.S. population projection (2015 - 2060) The results in the new projection show a growing share of population increase resulting from NIM as a part of the overall population increase. In 2015, NIM is projected to account for 47.3 percent of the increase. That is without including the share of population increase attributable to the children born to the immigrant population. By 2060, the CB projects that NIM will account for 78.8 percent of the overall population increase. This estimate is slightly lower than a 2008 estimate by Pew Hispanic researchers that 82 percent of U.S. population growth from 2005 and 2050 "...will be due to immigrants arriving from 2005 to 2050 and their descendants."
Because the CPS also reports an "other" category, and it varies widely by year and by location, we apportion that "other" amount among the other three categories (NIM, Births-Deaths, and Net Domestic Migration) in proportion to their shares.
Caveat:
The annual average estimates from CB data do not reflect the Decennial Census results that often reveal that the CPS population incorrectly estimated the size of the foreign-born population. When that happens, a new series of CPS estimates is based on the new data, but the previous CPS estimates are not revised. As a result there may be some variation between average annual change based on the Decennial Censuses and the change based on the CPS data.
In summary, the "adjusted" estimate of the impact of immigration on a jurisdiction includes:The "revised" estimate of the impact of immigration on a jurisdiction's population change is generic. It is not tailored to the specific jurisdiction's immigrant demographic characteristics such as age, nationality, education, religion, or other factors that could influence birth and death rates among segments of that population.
U.S. Immigration and Population
State Immigration and Population
Metro area Immigration and Population by state, and alphabetically