Accuracy and Coverage Evaluation (A.C.E.) Program in summer 2000. The A.C.E. matched the results of a survey of people residing in a set of randomly selected blocks to the set of census enumerations from those blocks and used the statistical method of dual-systems estimation to produce population estimates that could be used to adjust the census data.2

Redistricting—the redrawing of boundaries of congressional and other legislative districts to reflect population shifts—was the focus of the second major application decision regarding sample-based adjustment. The Census Bureau faced a legally mandated deadline of April 1, 2001, to release population counts at the block level for redistricting purposes. On March 1, the Census Bureau recommended to the U.S. Secretary of Commerce that unadjusted counts from the enumeration process should be the official data for redistricting; the secretary adopted the Bureau’s recommendation on March 6. The Bureau’s recommendation not to adjust the block-level counts was driven by the lack of time to resolve its concerns over the accuracy of disparate population estimates derived from the census, the A.C.E., and demographic analysis (a technique that constructs a national population estimate based on birth, death, and Medicare records, and estimates of net immigration).

The third major application decision on adjustment of the 2000 census is expected to occur on or about October 15, 2001, when the Bureau issues its recommendation on whether to adjust census data that are used to allocate state and federal funds and for other purposes. The Bureau has been conducting additional evaluations since March of the census, the A.C.E., and demographic analysis. It is at this juncture, between two critical decision points in the release of 2000 census data, that the Panel to Review the 2000 Census offers preliminary assessments of the census and A.C.E. processes.


Given the importance of the many uses of census data and the need to have an independent assessment of the quality of the 2000 census operations and results, the Census Bureau in 1998 asked the Committee on National Statistics (CNSTAT) of the National Research Council to convene a Panel to Review the 2000 Census. The panel has a broad charge to review the statistical methods of the 2000 census, particularly the use of the A.C.E. and dual-systems estimation, and other census procedures that may affect the completeness and quality of the data. A sister CNSTAT Panel on Research on Future Census Methods was convened in 1999 to begin consideration of the Census Bureau’s planning process for the 2010 census (see National Research Council, 2000a).

The panel has conducted several activities to date to carry out its charge. The panel held three open workshops on topics related to the A.C.E. and the


See the Glossary for definitions of such technical terms as dual-systems estimation.

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