generate a set of indirect estimates for one characteristic, say, the poverty rate, may not provide much information for the development of indirect estimates for another characteristic, say, employment. Third, if a multi-variate approach is used to exploit the correlations that exist among ACS estimates, the complexity of the modeling task is greatly increased. Consequently, a program to develop a large number of indirect estimates would take substantial time and resources. Yet the payoffs could be great from selected indirect estimates that are continuously updated for such purposes as fund allocation.

Seasonal and Multiple Residences

The long-form sample could not provide information on seasonal fluctuations in population, which characterize many localities, because it was conducted at a point in time and asked only about the location of the respondent’s usual residence. In contrast, the ACS is conducted continuously and asks respondents to employ a 2-month residence rule. The current data processing and estimation system for the ACS ignores the month-by-month information, producing instead period estimates for 1, 3, and 5 years that are controlled to census-based population and housing unit estimates as of July 1 of a specific year. However, the Census Bureau’s use of monthly data to produce pre– and post–Hurricane Katrina and Rita profiles for affected areas in the Gulf Coast demonstrates that it could be not only feasible, but also very valuable to produce such profiles for other areas.

To investigate the feasibility of producing part-year data for specified areas on a regular basis, the Census Bureau should conduct research on the extent to which the ACS monthly data exhibit significant seasonal variations in total population and key characteristics for localities expected to have such variations. It would be important to inform this analysis from the results of the test recommended by this panel and the Panel on Residence Rules in the Decennial Census on how respondents record their residence using the ACS 2-month rule compared with the census usual residence rule. This test may identify responses that do not accord with the 2-month rule that can be ameliorated by changes in question wording and instructions for the ACS.

The outcome of research on seasonal residence could be special data products for areas that have significant seasonal fluctuations, which would represent a major addition to the stock of useful information for them. One problem concerns sample size, given that seasonal change may be evident only for small areas. To the extent that seasonal patterns tend to be repeated each year, it would be possible, and likely essential, to combine multiple years of data in order to produce sufficiently precise estimates of part-year populations for affected areas.

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