Estimating the Undocumented Population:

A "Grouped Answers" Approach to Surveying Foreign-Born Respondents

GAO-06-775: Published: Sep 29, 2006. Publicly Released: Sep 29, 2006.

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As greater numbers of foreign-born persons enter, live, and work in the United States, policymakers need more information--particularly on the undocumented population, its size, characteristics, costs, and contributions. This report reviews the ongoing development of a potential method for obtaining such information: the "grouped answers" approach. In 1998, GAO devised the approach and recommended further study. In response, the Census Bureau tested respondent acceptance and recently reported results. GAO answers four questions. (1) Is the grouped answers approach acceptable for use in a national survey of the foreign-born? (2) What further research may be needed? (3) How large a survey is needed? (4) Are any ongoing surveys appropriate for inserting a grouped answers question series (to avoid the cost of a new survey)? For this study, GAO consulted an independent statistician and other experts, performed test calculations, obtained documents, and interviewed officials and staff at federal agencies. The Census Bureau and DHS agreed with the main findings of this report. DHS agreed that the National Survey of Drug Use and Health is not an appropriate survey for inserting a grouped answers question series.

The grouped answers approach is designed to ask foreign-born respondents about their immigration status in a personal-interview survey. Immigration statuses are grouped in Boxes A, B, and C on two different flash cards--with the undocumented status in Box B. Respondents are asked to pick the box that includes their current status and are told, "If it's in Box B, we don't want to know which specific category applies to you." The grouped answers approach is acceptable to many experts and immigrant advocates--with certain conditions, such as (for some advocates) private sector data collection. Most respondents tested did not object to picking a box. Research is needed to assess issues such as whether respondents pick the correct box. A sizable survey--roughly 6,000 or more respondents--would be needed for 95 percent confidence and a margin of error of (plus or minus) 3 percentage points. The ongoing surveys that GAO identified are not appropriate for collecting data on immigration status. (For example, one survey takes names and Social Security numbers, which might affect acceptance of immigration status questions.) Whether further research or implementation in a new survey would be justified depends on how policymakers weigh the need for such information against potential costs and the uncertainties of future research.

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