report. At this time we summarize briefly some of the important questions that must be dealt with in order to plan the decennial design.
Sample design and estimation procedures are intimately related to each other because the overall size and allocation of the sample in part determines what kinds of estimates will be feasible, while the estimation procedures conversely determine what the requirements are for the sample. One important issue is whether state population estimates will all be direct estimates, that is, estimates that use only data collected within that state. If this constraint is placed on the estimation procedures, then the sample must be designed so that every state has a large enough sample size to support a direct estimate of acceptable accuracy.
Current plans call for a sample size of approximately 750,000 households for integrated coverage measurement. This figure is calculated (Navarro, 1994) to make possible direct estimates with coefficients of variation of no more than 0.5 percent for states and for some important substate areas, such as major cities. The calculations appear in a series of internal Census Bureau memoranda from 1994-1995, which consider several different sample allocations with differing tradeoffs between the criteria of controlling the maximum standard deviation of the estimated population (which requires larger samples in the larger states) and controlling the maximum coefficient of variation (which requires roughly equal sample sizes in all states). We have not yet reviewed these issues closely, but we hope that the Census Bureau will prepare a more detailed discussion of sample allocation in time for the panel to give this closer attention in our final report.
The decision to allocate the sample size to support direct estimates for every state implies that the sampling rate--the ratio of sample size to state population--will be much lower in large states than in small ones, leaving little sample available for differential adjustment for substate domains (e.g., geographical regions in large states or urban compared with suburban and rural areas). This decision should be based on appropriate cost estimates. We also look forward to research on other features of the estimation procedure, such as the use of indirect estimates for substate domains.
Recommendation: The Census Bureau should perform the calculations necessary to clarify the effect of using direct state estimates on the sample sizes required for state estimates for the 2000 census and the consequences of these requirements for the accuracy of other estimates affected by integrated coverage measurement.
Fielding a large survey as part of the census will be a major challenge for the Census Bureau, but there is reason to believe that it will be possible. First, the management structure for the survey would be similar to that for the 1990 PES, which was successfully implemented by the regional offices. Second, the number of temporary staff in 2000 will be relatively lower than was required to implement the 1995 census test integrated coverage measurement (since the test had a much denser sample than is planned for the 2000 census), and the training and CAPI instrument will be better developed than in 1995. Since it was possible to do the necessary recruitment in 1995 even in the areas that are typical of those in which it is hard to recruit skilled personnel, it should be possible to do so in 2000.