unit controls are applied. At present the controls are applied at the estimation area, but they could alternatively be applied at higher or lower levels. If the postcensal estimates are of high enough quality, they could be applied at the level of the county or a subcounty area, such as a census tract, thereby targeting the adjustments more directly to the areas where they are needed. The Census Bureau has carried out some initial research in this area (Starsinic, 2005), and the panel encourages further research along these lines.


Recommendation 5-2: The Census Bureau should evaluate the quality of the postcensal housing unit estimates and the MAF sampling frame in relation to one another. In the light of this evaluation, the Census Bureau should assess the suitability of the current housing unit control factor adjustment and modify it as necessary.

The Census Bureau should attempt to identify areas in which improvements can be made to the postcensal housing unit estimates and to the MAF sampling frame. In particular, it should investigate an integrated approach for developing the postcensal housing unit estimates and for continuously updating the MAF that would benefit both and reduce the variability in the housing unit control factor.

5-D
POPULATION CONTROLS

After the application of the housing unit controls in step 5, each household has a weight that can be used for analysis, and that same weight could be used for each person in the household. Step 6 in the process is an adjustment to the person weights. This adjustment is used to compensate for person noncoverage in sampled households and to reduce the sampling errors for person-level estimates. The adjustments are based on the Census Bureau’s PE subnational resident population estimates by age, sex, race, and Hispanic origin for July 1 each year. For these estimates the resident population in an area is defined using the decennial census “usually resident” rule as distinct from the ACS “2-month resident” rule.

As with the PE housing unit estimates, the population estimates start from the 2000 census counts and adjust for estimated changes between April 1, 2000, and July 1 of the year in question. At the outset, the 2000 census population is divided into the household population and the group quarters population. For the 2005 ACS, the population controls are based on only the household population estimates, and only the methodology for developing those estimates will be reviewed here.

The Population Estimates and Projections Area of the Population Division at the Census Bureau produces county household population estimates using a cohort-component technique that adjusts the census counts to allow for births, deaths, net international migration, net domestic migration, and



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