It is also important to continue investigation of the reasons for errors in the census. In particular, it is important to learn as much as possible about census operations that may have contributed to duplicate enumerations and imputations in order to identify useful modifications to census procedures for 2010.

Finally, we stress that there will always be a need to evaluate the adequacy of population coverage in the census and to have a basis for census adjustment if needed. For this reason, it is essential to continue research on ways to improve the A.C.E., as well as the census.

In all of these analyses, the Census Bureau can benefit from the contributions and insights of independent researchers. The panel urges the Bureau to make available as much A.C.E. and census data as possible to the scientific research community for evaluation purposes. The Bureau should develop publicly available analysis files (consistent with protecting confidentiality) of coverage-related information (e.g., imputations, reinstated people, match rates) for post-strata and geographic areas. It should also find ways to provide access to A.C.E. microdata for researchers. While the likely errors in the A.C.E. preclude the use of the data for adjustment purposes at this time, there is much value in the data for research.


In its work to prepare a final report, the panel plans to address the quality of the important socioeconomic information collected in the census long form and to review the detailed information obtained on race and ethnicity. The panel will also review further Census Bureau evaluations of population coverage in the 2000 census and consider methods for improving coverage evaluation for future censuses.


The panel concludes that the Census Bureau’s two decisions (March and October) not to adjust the 2000 census counts for coverage errors are justifiable because of the evidence of errors in the A.C.E. that could lead to overstating the population.

The panel concludes that the Bureau’s estimates of the effects of the unmeasured erroneous census enumerations on net undercount rates for population groups are far from definitive. These estimates are based on small samples and incorporate a number of simplifying assumptions. The Bureau should conduct further research on the unmeasured duplicate and other erroneous census enumerations and attempt to develop revised estimates of net undercount for the population and for major population groups. The Bureau should also conduct further research on the causes, quality, and effects of the larger number

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