There has been much speculation about the adequacy of the immigration component used in the DA estimates. Passel (2001) argues that data now available support a significantly higher estimate of undocumented immigrants in the population in 2000 than that used by the Bureau. Specifically, looking at the March 2000 CPS foreign-born estimates, Passel concludes that one can easily support an estimate of undocumented immigrants of 7 million, which is 1 million higher than the DA base estimate. Furthermore, using 2000 census and A.C.E. data to adjust the March 2000 CPS would support even higher estimates of undocumented immigrants—perhaps in the 8–9 million range. Some recent work by Warren (2001), released by the Immigration and Naturalization Service, supports an estimate of 6.5 to 7.5 million undocumented immigrants in the United States at the time of the census—higher than the DA base estimate but lower than Passel’s high estimates. Recently released data from the Census 2000 Supplementary Survey supports Passel’s higher estimates of 8–9 million undocumented immigrants in the United States in 2000.⁶

Passel’s research also suggests that the Census Bureau understated two components of legal immigration: foreign-born people living in the country legally with temporary visas (e.g., foreign-born students and guest high-tech workers) and Mexicans living in the United States as legal residents. According to Passel, both of these groups increased in number during the 1990s more than indicated by data on legal admissions. Reasonable estimates for these two groups would add about another 750,000 people to the estimates. Furthermore, there are indications that the Bureau’s allowances for net emigration may have overstated the number of immigrants who left the country during the 1990s.⁷

In response, the Census Bureau has suggested that these higher estimates of legal and illegal immigrants imply that the proportions of foreign-born people in the U.S. population—particularly Hispanics—are much higher than are reasonable based on past history. Bureau researchers are currently looking at detailed information from the 2000 census long form and the Census 2000 Supplementary Survey on country of birth, year of immigration, and other characteristics to try to resolve competing estimates of legal and illegal immigrants.

This discussion is not intended to answer the question of the quality of the DA estimate, but rather to point out the problem of fine-tuning and interpreting the DA estimate in light of the uncertainty associated with estimates of the immigration (legal and illegal) components. As already noted, there are no precise tools for evaluating the accuracy of DA. Rather, one uses analyses of such