Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2015-January 2018 [open pdf - 856KB]
From the Introduction: "This report presents estimates of the size of the unauthorized immigrant population residing in the United States on January 1 each year from 2015 through 2018. The results are tabulated according to available demographic characteristics, including period of entry, country of origin, state of residence, age, and sex. As in previous editions, the estimates were calculated using the residual method in which the unauthorized population is the remainder (or residual) after the legally-resident, foreign-born population--naturalized citizens, lawful permanent residents (LPRs), asylees, refugees, and certain nonimmigrants--is subtracted from the total foreign-born population. The legally-resident subpopulation was estimated primarily based on the Department of Homeland Security's (DHS) administrative records and modeled components of population change (such as emigration and mortality), and the total foreign-born population estimate was derived from the American Community Survey (ACS) of the U.S. Census Bureau with adjustments for undercount and the choice of reference date. The population must be estimated because there is no nationally representative survey or census that includes information on the legal status of foreign-born residents."
Department of Homeland Security: http://www.dhs.gov/