This assumed that, for each country of origin, undocumented immigrants who resided in the United States in October 1992 had the same U.S. residence pattern as IRCA applicants from that country. The revised and updated estimates presented here incorporate the same assumption for the October 1988 undocumented population. However, it was necessary to develop new methods of deriving state estimates for October 1992 and 1996 that would reflect more recent patterns of geographic settlement. As noted, the estimates of the undocumented population were constructed separately for overstays and EWIs. This permitted the distribution of the overstay and EWI populations to states using data most appropriate for the type of population.
Limitations Estimating the size of a hidden population is inherently difficult.
Overall, the figures presented here generally reflect the size, origin, and geographic distribution of the undocumented immigrant population residing in the United States during the mid-1990s. The estimates probably reduce the range of error for the total population to a few hundred thousand rather than a few million, which was the error range during the late 1970s and into the 1980s. The estimates for most countries should be fairly precise because they were constructed primarily from data on nonimmigrant arrivals, departures, and adjustments of status that have relatively small margins of error. Although the estimates are based on the most reliable information available, they clearly have limitations. The figures for some countries overstate the actual undocumented population.