would still not meet commonly accepted standards of precision or even the levels of precision of the long-form sample. They would, however, be 25 percent more precise than comparable estimates from the current ACS.

Recognizing fiscal constraints, increases in the ACS sample size would likely have to be made on an incremental basis. Eliminating the institutional group quarters population from the ACS, as suggested in Section 4-C below, could permit a small increase in the household sample size within the current budget. It is also possible that making school districts ineligible for oversampling would permit some redistribution of the sample to other types of small governmental units.

The panel urges the Census Bureau to work closely with the user community to identify and assess the merits of alternative sample sizes and designs for the ACS. It is unlikely that any single design will be optimal for all users, so that trade-offs and compromises will be necessary, as is true of the current design.

Recommendation 4-4: The Census Bureau should identify potential ways to increase the precision of ACS estimates for small geographic areas, particularly small governmental jurisdictions, through reallocation of the sample and through increases in the overall sample size. Cost savings should be sought to support such increases, although increases that could significantly improve the precision of estimates will require additional funding from Congress. Sample reallocation should also be considered to minimize anomalies across areas (for example, jurisdictions with very similar populations that fall into different sampling rate categories).


Mode of Collection

The ACS, like many surveys, uses a mixed-mode data collection design in order to maximize response while containing costs. The ACS uses three modes of data collection:

  1. mailout-mailback, assisted by an advance letter, postcard reminder, and second questionnaire mailed to nonrespondents;

  2. CATI from three telephone call centers to try to reach mail non-respondents (the telephone is also used to follow up mail respondents for whom edit checks indicate a problem with the coverage of household members or failure to answer a minimum number of items); and

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