Revised Method for Estimating the Resident Unauthorized Immigrant Population in the United States

Nancy Rytina, U.S. Department of Homeland Security (DHS)
Michael Hoefer, U.S. Department of Homeland Security (DHS)

Using a revised version of the residual method pioneered by Robert Warren and Jeffrey Passel, the Department of Homeland Security released new estimates of the unauthorized resident immigrant population for January, 2005. Our goals were to make as few simplifying assumptions as possible, be transparent, and take advantage of our internal expertise on administrative immigration data. The 2005 estimates are the first of a planned annual series to be based on the Census Bureau’s American Community Survey (ACS) for estimating the foreign born population and DHS administrative data for estimating the legally resident. In this paper, we explain our methodology in greater detail than was included in our report that was released. We focus on the assumptions that generate the most uncertainty in the estimates and quantify their impact. We also discuss options for improving the estimates.