The Department of Homeland Security is required to submit a report to Congress each year on trends in immigration and naturalization, including how many people are unlawfully present in the United States.
DHS’s report of December 2018 estimated 11.96 million foreign-born individuals were unlawfully residing here as of January 1, 2015.
We reviewed DHS’s March 2019 report which listed 8 approaches that could improve its annual estimates, such as using more precise mortality estimates for foreign-born populations rather than standard demographic tables. It noted that it did not assess the costs and benefits of these approaches.
Homeland Security sign
What GAO Found
The Department of Homeland Security (DHS) identified various limitations to its estimates of the unlawfully resident foreign-born population in the United States, and eight possible approaches the department or other entities could take to improve the estimates. DHS uses a residual estimation methodology, which consists of subtracting the estimated legally resident foreign-born population (derived from DHS administrative data) from the estimated total foreign-born population (derived from the U.S. Census Bureau’s American Community Survey) to produce an estimate of the unlawfully resident population. DHS officials and stakeholders identified the limitations that most significantly impact DHS’s estimates to be uncertainty regarding the size of the American Community Survey undercount (nonrespondants), which affects the estimate of the total foreign-born population, and uncertainty regarding emigration rates of foreign nationals, which affects the estimate of the legally resident foreign-born population. DHS also reported limitations related to foreign national mortality data, which also affect the estimates of the legally resident foreign-born population, and other limitations.
In its March 2019 report, Potential Improvements to DHS Illegal Alien Population Estimates: Collection and Use of Data, DHS identified eight possible approaches to improve its estimates of the unlawfully resident population. Some approaches address limitations DHS and stakeholders identified as the most significant, and others aim to improve DHS data systems to strengthen DHS’s population estimates and improve its overall immigration reporting and analysis. For example, one approach DHS proposed is for the U.S. Census Bureau or a private sector entity to assess the American Community Survey undercount of foreign-born populations which, according to DHS officials, could improve DHS estimates by providing a more accurate basis for its estimate of the total foreign-born population. Other proposed approaches, such as assigning unique identifiers to nonimmigrants in DHS data systems and capturing more immigration data electronically, could, according to DHS officials, refine and add descriptive information about DHS’s legally resident population estimates, but would not affect total estimates of the unlawfully resident population. DHS has ongoing work that should help implement three of the eight approaches, and proposed coordinating with outside entities to implement four of the five approaches not underway.
Why GAO Did This Study
DHS has the primary responsibility for collecting and disseminating statistical information and analysis used in evaluating the impacts of immigration laws, migration flows, and immigration enforcement. Consistent with a requirement in the Immigration and Nationality Act that DHS estimate the population of foreign nationals who are unlawfully present in the United States, DHS publishes annual estimates of the population of foreign-born persons who are unlawfully residing in the United States. DHS’s Office of Immigration Statistics (OIS) publishes annual estimates of the number of foreign-born persons who are residing in the United States without lawful immigration status. In December 2018, OIS reported an estimated 11.96 million foreign-born individuals were unlawfully residing in the United States as of January 1, 2015.
The Explanatory Statement accompanying the Consolidated Appropriations Act, 2018, directed DHS to report within 180 days after enactment on how to improve its collection and use of data sets necessary to develop an estimate for the entire population of those illegally present in the United States. The Explanatory Statement also included a provision for GAO to review DHS’s report and provide a preliminary briefing to the House and Senate Appropriations committees on its review within 90 days after DHS’s report was provided to the committees. This report transmits, in the form of the enclosed briefing, our assessment of DHS’s report and its findings that we provided to you electronically on June 3, 2019.
This report examines limitations DHS identified in its estimates of the unlawfully resident population and how DHS plans to improve its estimates. GAO analyzed OIS reports presenting annual estimates of the foreign-born population unlawfully residing in the United States from 2006 (the first year DHS reported estimates) through 2018; DHS’s March 2019 report discussing possible ways to improve the estimates; and prior GAO reports, academic literature, and think tank publications. GAO also interviewed OIS officials to discuss the limitations DHS identified, how the limitations affect the estimates, and the implementation status of the approaches DHS identified for improving the estimates. In addition, GAO interviewed officials from the Pew Research Center and the Center for Migration Studies to discuss their estimates of the unlawful population; and researchers DHS officials identified as undertaking research that could help inform the approaches DHS proposed. GAO obtained perspectives from these stakeholders on limitations to current estimation methods and how the estimates could be strengthened.
For more information, contact Rebecca Gambler at (202) 512-8777 or GamblerR@gao.gov.