Illegal Aliens: Despite Data Limitations, Current Methods Provide Better Population Estimates

PEMD-93-25 Published: Aug 05, 1993. Publicly Released: Aug 31, 1993.
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Pursuant to a congressional request, GAO: (1) examined federal methods for estimating the size and flow of the illegal alien population in the United States; (2) combined estimates with other data to narrow the range of estimates; and (3) identified ways to more accurately measure the illegal alien population.

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Recommendations for Executive Action

Agency Affected Recommendation Status
Immigration and Naturalization Service The Commissioner of the Immigration and Naturalization Service should ensure that INS further explores ways in which Census Bureau data can be used to improve information on the foreign-born population, including illegal aliens and special agricultural workers, with as much geographic detail as possible, such as estimates of the distribution of this population across states and metropolitan areas. A detailed analysis by age, country of birth, and period of entry would be needed to produce such estimates. Also INS could use the information on legal immigrants to assist in meeting its reporting requirements specified in the Immigration and Nationality Act.
Closed – Implemented
INS has a number of initiatives under way with the Census Bureau to improve statistics on immigration, including one that provides data on country of birth and year of immigration. It is not clear how much geographic detail will be supported by these efforts, however.
Immigration and Naturalization Service The Commissioner of the Immigration and Naturalization Service should ensure that INS works with the Census Bureau to improve the coverage of the foreign-born in the Current Population Survey, including the Bureau's planned analysis updating estimates of those foreign-born persons permanently leaving the United States. This information would help to improve national population estimates as well as provide a more current basis for estimating the total foreign-born population (and hence, the number of illegal aliens) in the future. Also further emigration supplements using the regularly collected foreign-born data in the Current Population Survey could provide a continuing update of this important component of population change.
Closed – Implemented
INS took the lead in ensuring that questions on nativity were included in the monthly CPS, beginning in 1994. These data are available to researchers on request. INS and Census are continuing to work on new estimates of immigration.
Immigration and Naturalization Service The Commissioner of the Immigration and Naturalization Services should ensure that INS works with the Secretary of Health and Human Services to assess the feasibility of conducting research on the birth and death rates that apply to the foreign-born population through sample surveys of both the vital events themselves and the population bases. These data, if collected by age group, could be combined with the estimates of the counted illegal alien population and, by implication, measure the uncounted illegal alien population.
Closed – Not Implemented
INS consulted the Interagency Working Group on Immigration Statistics. It decided not to pursue this line of research because other methods appeared to provide better estimates of the illegal alien population.
Directorate of Border and Transportation Security To improve the collection of departure forms, The Commissioner of the Immigration and Naturalization Service should ensure that INS examines the quality control of the Nonimmigrant Information System database and determine why departure forms are not being recorded. For example, this could involve examining a sample of the passenger manifest lists of flights with foreign destinations to determine the extent of airline compliance and possibly developing penalties on airlines for noncompliance. Discovery of the incidences of various causes of departure loss could allow more precise estimation of their occurrence and development of possible remedies.
Closed – Implemented
On October 30, 2008, DHS representatives told GAO of their plans to study the collection of departure information in a pilot program at 10 airports. On June 10, 2009, Ginny Pollack, CBP Audit Liaison, Office of Policy and Planning, U.S. Customs and Border Protection (202) 344-3428, sent GAO a summary of results of this pilot program (Doc #3128264) with supporting documentation (Doc #3128284 and Doc#3128284) for the most recent activities that had been completed. DHS (1) conducted a study of departure information collection, and (2) did so directly in response to our recommendation; thus, DHS was responsive to the recommendation and the recommendation should be closed. At the same time, we note that DHS's study of this issue is still somewhat limited; notably, although the DHS study does check departure records against independently obtained data, it does not address the difficult question of whether an acceptable percentage of recorded entries to the U.S. can be matched to departure records.
Immigration and Naturalization Service The Commissioner, INS, should ensure that INS regularly tabulates the Nonimmigrant Information System database to identify long-term visa overstays. These data will be valuable in showing the net growth of the illegal alien population through overstaying as well as developing profiles of those most likely to remain in the country illegally.
Closed – Implemented
INS reports that it is now providing regular tabulations of NIIS and is working on automating data collection in the NIIS database. If successful, this would provide more accurate and timely data.
Directorate of Border and Transportation Security If INS decides to implement the new Software Assisted Screening System for fingerprint identification, currently being tested by the Border Patrol to identify individual aliens apprehended, the Commissioner of the Immigration and Naturalization Service should ensure that the processing capability could be implemented for statistical tabulations of the data to be made publicly available on a regular and timely basis. Data from this system could assist not only in enforcing the law, but also in estimating the flow of illegal aliens by providing information on the number of distinct individuals apprehended, the frequency of apprehension, the time between apprehensions, and the probability of apprehension. These data, provided periodically, will assist in making estimates of the flow of border-crossing illegal aliens. Once a database of individuals who attempt entry is established, monthly tabulations of this system could be very useful by providing timely information on the number of additional individuals who are apprehended. Data on the characteristics and origin of those attempting illegal entry could be used not only to improve estimates of the flow of illegal aliens, but also to continue to formulate policy addressing the causes of illegal migration to the United States.
Closed – Not Implemented
INS' operations were transferred to the Department of Homeland Security on March 1, 2003, and on July 31, 2003, GAO interviewed the ENFORCE/IDENT Program Manager, who is now in charge of the IDENT system. (ENFORCE refers to Border Patrol enforcement and IDENT refers to the automated fingerprint system used to record information about individuals who are caught attempting to illegally enter the United States; both are part of the US-VISIT program office and report directly to the Directorate of Border and Transportation Security). The ENFORCE/IDENT Manager told GAO that after consulting managers at the National Security Unit and the Compliance Enforcement Unit and requirements of the IDENT program, he concluded that publishing or publicly releasing IDENT statistics could compromise ongoing law enforcement efforts to control illegal immigration and that he declines to publicly release or publish such statistics on grounds that doing so would compromise national security. He noted that the Department of Justice Inspector General had, even before September 11, declined to publish IDENT statistics because doing so could compromise law enforcement efforts to control illegal immigration. GAO told the ENFORCE/IDENT Manager that his concerns seem reasonable and that this recommendation would be changed to "Closed Not Implemented" on grounds that complying with it could compromise national security in light of September 11.

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