areas from the use of different population groups (poststrata) for estimating erroneous census enumerations and census omissions. In addition, there is a large discrepancy in coverage estimates for children ages 0–9 when comparing demographic analysis estimates with Revision II A.C.E. estimates (2.6 percent undercount and 0.4 percent net overcount, respectively).

Finding 6.4: Demographic analysis helped identify possible coverage problems in the 2000 census and in the A.C.E. at the national level for a limited set of population groups. However, there are sufficient uncertainties in the revised estimates of net immigration (particularly the illegal component) and the revised assumption of completeness of birth registration after 1984, compounded by the difficulties of classifying people by race, so that the revised demographic analysis estimates cannot and should not serve as the definitive standard of evaluation for the 2000 census or the A.C.E.

Finding 6.5: Because of significant differences in methodology for estimating net undercount in the 1990 Post-Enumeration Survey Program and the 2000 Accuracy and Coverage Evaluation Program (Revision II), it is difficult to compare net undercount estimates for the two censuses. Nevertheless, there is sufficient evidence (from comparing the 1990 PES and the original A.C.E.) to conclude that the national net undercount of the household population and net undercount rates for population groups were reduced in 2000 from 1990 and, more important, that differences in net undercount rates between historically less-well-counted groups (minorities, children, renters) and others were reduced as well. From smaller differences in net undercount rates among groups and from analysis of available information for states and large counties and places, it is reasonable to infer that differences in net undercount rates among geographic areas were also probably smaller in 2000 compared with 1990. Despite reduced differences in



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