AN ANALYSIS OF NET IMMIGRATION IN CENSUS COVERAGE EVALUATION

National surveys monitored growth in the foreign-born population for the 1980s, especially net undocumented migration's continuing role, but the 1990 census portrayed an even larger foreign-born population than these surveys. Undercoverage in 1990 could have been higher than initially presented because preliminary studies may have insufficiently accounted for decadal net immigration. Assumptions intended to maintain a high undocumented undercount performed poorly when census counts of foreign-born residents became known. Any point estimate for net undocumented migration, calculated as a residual, is likely to be biased by assumptions and data gaps for components of calculating net legal immigration, especially in the direction of underestimation. A reasonable statement is that at least 2.1-2.4 million undocumented residents were enumerated in the 1990 census. The number of unenumerated undocumented residents may easily have ranged between 0.5 million and 3.0 million, and a narrower range of 1 million to 2 million is plausible. Despite the importance of undocumented migration measurement for census evaluation and policy purposes, differences among various undocumented estimates are more likely to stem from discrepancies in universe, reference dates, or individual judgment, rather than analytic refinement. Better measurement of the foreign-born population or its census coverage would aid in setting upper limits on net undocumented migration.