further study, that the A.C.E. population estimates were too high and an adjustment using A.C.E. results as originally calculated would have overstated the population.

We view the Bureau’s March 2003 conclusion as justified because the final A.C.E. estimates that it produced from further analysis, while reflecting high-quality, innovative work, had to make use of incomplete data and incorporate assumptions that cannot be well supported.

Although the A.C.E. Program experienced problems, the program and its supporting research provided important insights into the census process. Moreover, the 2000 A.C.E. experience reaffirmed the utility of in-depth assessment of both coverage gaps and duplications.

Finding 1.6: The Accuracy and Coverage Evaluation Program provided invaluable information about the quality of the 2000 census enumeration. The A.C.E. was well executed, although problems in reporting Census Day residence led to underestimation of duplicate census enumerations in the original (March 2001) A.C.E. estimates.

In the panel’s assessment, the 2000 census and A.C.E. experiences suggest three basic findings (or conclusions): first, on the need to examine components of gross error, as well as net coverage error; second, on the need for adequate time to evaluate the completeness of population coverage and the quality of data content; and, third, about the root variability of census totals at the finest grained geographic level.

Finding 1.7: The long-standing focus of key stakeholders on net undercount distracts attention from the components of error in the census, which include duplications, other erroneous enumerations, and omissions. Although the most recently released national net undercount estimate for 2000 is a small net overcount of 0.5 percent of the population (1.3 million additional people counted), there were large numbers of gross errors, almost as many as in



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