the development and implementation of an improved A.C.E. Program for the 2010 census. The A.C.E. survey in 2010 should be large enough to provide estimates of coverage errors that provide the level of precision targeted for the original (March 2001) A.C.E. estimates for population groups and geographic areas. An important area for improvement is the estimation of components of gross census errors (including types of erroneous enumerations and omissions), as well as net error. Understanding gross errors is valuable for identifying areas for improvement in census processes. Other important areas for improvement include the inclusion of group quarters in the A.C.E. (they were excluded in 2000); improved questionnaire content and interviewing procedures about place of residence; a simpler procedure for treating people who moved between Census Day and the A.C.E. interview; the development of poststrata for estimation of net coverage errors by using census results and statistical modeling as appropriate; and the investigation of possible correlation bias adjustments for additional population groups (Recommendation 6.1). We also recommend that the Census Bureau strengthen its program to improve demographic analysis estimates, particularly estimates of net immigration and measures of uncertainty for the demographic results (Recommendation 6.2).

It is clear from the experience with the 2000 A.C.E. that evaluation of coverage errors in the census takes time. It also takes time to evaluate census processes and the quality of the census data for individual items. In the panel’s view, adequate evaluation of the census block-level data for congressional redistricting is not possible by the current deadline. Congress should consider moving this deadline to allow more time for evaluation of the completeness of population coverage and quality of the basic demographic items before they are released (Recommendation 6.3). Users should be aware that census counts at the block level—whether based on the enumeration or adjusted for coverage errors—are subject to high levels of variability; these data should be aggregated to larger geographic areas for use.

ASSESSMENT OF COMPLETE-COUNT AND ADDITIONAL LONG-FORM-SAMPLE DATA

The 2000 census data for items asked of everyone (age, sex, race, ethnicity, household relationship, housing tenure) were quite complete at the national level—missing data rates ranged from 2 to 5



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