A New Residual Approach for Estimating Undocumented Populations

Demographers generally agree that the total undocumented population in the United States increased from 3.5 million in 1990 to about 12 million in 2008 and declined from 2008 to 2010. The consensus breaks down after 2010, however, with three of the five organizations that derive annual estimates of the population showing increases from 2010 to 2018 and two organizations reporting substantial declines over the period. The primary reason for this divergence is that organizations use a variety of estimates of emigration of legal residents, and in some cases the data are decades out of date. Reliable information about trends in this population is important for developing legislative and administrative policies to reduce the population and for assessing the effectiveness of enforcement efforts. This research note describes an improved residual method for updating annual estimates of the undocumented population counted in the American Community Survey (ACS; Ruggles et al. 2022); the method incorporates a time-varying estimate of emigration. Data needed to update estimates are available in the year estimates are derived, and a new estimate can be compiled as soon as ACS data are released. The methodology and data needed to update an estimate of the undocumented population each year are described.