groups will often meet common standards of precision for areas of 50,000 population (see Table 2-8). Moreover, 50,000 is a common threshold for allocation of various types of federal assistance. Yet another advantage of lowering the threshold to provide 1-year period estimates for additional areas is that users would have more flexibility in combining the data and, consequently, would less often have to request special tabulations from the Census Bureau. For example, users could average two 1-year period estimates for a small city or county to obtain a 2-year period estimate that was more precise than the individual 1-year period estimates.

A second issue for release of geographic area tabulations concerns the feasibility of producing 3-year period estimates for user-defined statistical subareas of large cities and counties. Such subareas could be a set of aggregations of census tracts or block groups in cities and of places and towns in counties, where the city or county has at least 40,000 people (so that, at a minimum, there are two subareas, each with at least 20,000 people). If the city or county is large enough to have more than one PUMA, then the subareas could usefully nest within a PUMA to maximize the ability to relate the data for the PUMA and its subareas. (PUMA boundaries may need to be redrawn in some areas to achieve the most useful designation of subareas within PUMAs.) Finally, it may be possible to produce 1-year period estimates for large statistical subareas of PUMAs, particularly if the threshold for 1-year period estimates is lowered to 50,000 people. The Census Bureau will need to explore with users the desirability of providing additional estimates for statistical subareas of large cities and counties and weigh user needs against the feasibility of increasing the production workload for the ACS.

Recommendation 4-12: If some or all GQ residents continue to be included in the ACS, the Census Bureau should consult with users regarding the most useful population universe for tabulations, which, depending on the table, could be the entire population, the household and GQ populations separately, or the noninstitutional and institutional populations separately.

Recommendation 4-13: The Census Bureau should consider expanding the geographic areas for ACS tabulations in order to afford users greater flexibility for aggregating small areas into larger user-defined areas. Two possibilities to investigate are to lower the population threshold for 1-year period estimates to, say, 50,000, and to produce 3-year (and possibly 1-year) period estimates for user-defined statistical subareas of large cities (aggregations of census tracts or block groups) and counties (aggregations of places and towns).

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