Small Populations, Large Effects Improving the Measurement of the Group Quarters Population in the American Community Survey (2012) / Chapter Skim
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. Although the ACS collects social and economic data on the characteristics of the GQ population, the GQ sample size is not large enough to produce accurate estimates of the characteristics of the GQ population for small geographic areas, and such estimates are not published.
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The lack of accurate data about the GQ population can adversely affect the ACS estimates produced for such places and, generally, for small geographic areas, especially because GQ residents tend to be systemati cally different from the household population in the communities where they live. Moreover, the fact that many geographic areas have none of their GQ facilities included in the ACS sample can substantially alter the characteristics of the total population year by year, even in small communities where GQ facili ties represent only a small proportion of the total population.
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Yet these adverse effects are masked because detailed characteris tics data are not published separately for the GQ population. Moreover, due to the relatively small overall ACS sample size, a substantial number of counties and smaller geographic areas with actual existing GQ populations within their boundaries have no GQ residents represented in the sample.
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, such as modeling or imputing some of the GQ data, and these could also have the potential of improving the GQ estimates significantly at lower cost. The Census Bureau already has conducted research on methodological issues for group quarters; in particular, it has investigated imputation methods for improving the ACS estimates of GQ residents and total population for small geographic areas, and plans to implement a new imputation method for the GQ data that it collects in 2012 and beyond.
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Census Bureau divisions that develop frames for sampling particular GQ types for other federal agencies; and 3. other federal agencies that may have information on particular types of group quarters.
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with the housing unit sampling frame and, in tandem, modifying its data collection procedures to enable field representatives to collect data from all cases -- housing unit and group quarters -- in the com bined sample. Additional research will be needed to determine which GQ types are best suited for integration with the housing unit sample, but the GQ types that are especially difficult to update and that are most similar to housing units may be the best candidates.
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Recommendation 5-1: The Census Bureau should conduct a formal evalu ation of sample redesign strategies that would make it possible to control the American Community Survey group quarters sample allocation at the substate level. The evaluation should focus on identifying options that can improve the precision of the estimates at the state and substate levels with out substantially increasing the costs of the data collection.
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This means that although the ACS sample does not include a sufficiently large num ber of group quarters overall for accurate estimates for small geographic areas, some large GQ facilities can have multiple groups of 10 residents in the sample. This strategy is less costly in terms of data collection operations than including a larger number of group quarters in the sample with fewer residents in each, but it may be statistically inefficient because group quarters provide housing and services to people with similar needs and circumstances, and the intraclass correlations within group quarters are naturally high for many variables.
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The state-based sample design of the ACS is not an efficient vehicle for providing substate estimates of the GQ population, and the estimates can be especially error prone in small areas where the GQ population represents a large portion of the total population. Many small areas are missing group quarters in the sample entirely.
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LOOKING TO THE FUTURE The process of improving estimates of the group quarters and total populations for small geographic areas in the American Community Survey will need to involve not only continued research and development by the Census Bureau but also regular feedback from data users. It is the panel's observation that data users are not yet familiar with the properties of the 5-year ACS estimates for small geographic areas and the limited information that can be provided specifically for GQ residents.
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