more timely completion of nonresponse follow-up will permit the coverage measurement survey to be implemented in the field closer to census day, thereby decreasing recall errors and the effect of people who move on the process of coverage measurement and correction. Second, the use of sampling will make it possible to use better qualified and more highly trained personnel to conduct the nonresponse follow-up work.
We stress again, as we did in our first interim report, that it would not be feasible to implement the intensive procedures that would be needed to significantly improve census coverage without the use of sampling. The initial census process itself will use the best methods possible to identify every household in the country and the best techniques available so that householders can provide information about all residents of the household. Yet experience in recent censuses clearly shows that the number of people missed as a result of missed dwellings and of people missed in enumerated dwellings is too great and, in particular, too inequitably distributed to be ignored if a census is to be of adequate quality. Thus, to conduct an adequate census, sampling procedures must be used and the results integrated into the final population counts.
Although sampling procedures to "complete the count" have not been used previously in a decennial census (either for nonresponse follow-up or for coverage measurement), the procedures proposed are well established in the production of official statistics and in the conduct of scientific research. Indeed, there is widespread public confidence in the data collected by the census long form, which is on a sample basis from 1 in 6 households in 1990. Such sampling for expanded information began in the 1940 census. Probability sampling procedures are acknowledged to be an objective method of collecting data from which it is possible to obtain valid measures of the level of variability introduced as a result of using a sample.
The exact procedures for implementing sampling and its associated estimation procedures, both for nonresponse follow-up and for coverage measurement, must be scientifically established on the basis of available evidence. The panel finds that the Census Bureau is using such an approach to develop its procedures. The final procedures to be used must be shared with knowledgeable data users and other interested parties and must be clearly established prior to the conduct of the census. With this approach, the use of sampling in enumerating the population will be demonstrably free from influence aimed at achieving a particular result in a given geographic area.
There are several objections that have been raised about the use of sampling as part of census procedures. Some concerns are legal: we do not attempt to address those, which are largely outside the panel's area of expertise. We do note, however, that like a previous panel (Edmonston and Schultze, 1995) we have not seen evidence of any prevailing or significant legal opinion that the use of sampling, in the manner contemplated by the Census Bureau, would result in a census that did not fulfill constitutional requirements.