population counts. This procedure placed the Census Bureau in the position of having to decide whether or not to use the analysis when its effects were already known. The director of the Census Bureau recommended using that analysis to adjust the 1990 census, based on a technical assessment that this would improve the overall accuracy of the census counts, but the Secretary of Commerce did not accept the recommendation. Much valuable experience was gained from this first full-scale attempt to implement coverage measurement and adjustment in the census.
Current plans for the 2000 census call for full integration of coverage measurement into the census process (Bureau of the Census, 1996a). Major decisions about methodology for measuring coverage of the initial census operations (mail-out/mailback returns, nonresponse follow-up, "Be Counted" forms, etc.) and for including the results of coverage measurement in the final counts will be made before the census. Therefore, there will be a single set of census numbers (a "one-number census") rather than a decision on which of two sets of numbers to use after the census. To emphasize the interdependence of all aspects of the census process, the coverage measurement component of the procedure is called ''integrated coverage measurement." The Census Bureau's intention is to do an adequate evaluation of the methodology before the census so that the quality of the integrated coverage measurement can be determined before the census and the decision can be made in advance on whether to incorporate its results into the final enumeration. The advantages of this approach include better timing (no need to allow time in the schedule for making a decision between the initial census results and the release of the final counts), more efficient and focused census operations (no need to pursue two tracks simultaneously), and greater acceptability (because the main decisions on methods are made before their consequences for particular groups or areas are known).
Integrated coverage measurement subsumes both the data collection operations that measure coverage and the estimation procedures that bring the results into the enumeration. Integrated coverage measurement is intended to measure and correct differences in census undercoverage across fairly broad domains. These domains could, for example, be major geographic regions or states; urban, suburban, and rural parts of a geographic region; or subgroups by race and Hispanic origin. These are the levels at which systematic differences in coverage have been found to occur and to persist over time. Integrated coverage measurement is not intended to measure and correct relatively local differences in coverage, such as those occurring in particular localities (except, perhaps, in a few very large cities that are comparable in size to states); the costs and limitations of technical resources do not permit extremely detailed local corrections. Allocation of population to these very small domains depends on the mail-out/mail-back responses together with the nonresponse follow-up. However, integrated coverage measurement domains can be much more detailed geographically than those for which reliable demographic analysis estimates can be obtained. A general discussion of