“without making restrictive assumptions about within small area variance” to produce more efficient estimates of poverty and housing unit characteristics than could be could be made directly.4

The value added from data linking thus stems from two factors. First, national surveys, such as the CPS supplements, include a limited number of variables for studying specific topics. Linking datasets allows for a broadening of covariates that may be correlated with measures of outcomes. Combining individual-level survey information with data from other sources can provide contextual information about counties, districts, and states that may be useful explanatory variables. Second, and very relevant to the CPS Civic Engagement Supplement, is that sample sizes associated with national level population surveys are not typically adequate to support local area analyses.

CONCLUSION 8: The Current Population Survey (CPS) cannot provide all the variables and the level of geographic detail necessary for research on social capital, social cohesion, and civic engagement. It is therefore essential that design strategies for the CPS be conceptualized with the presumption that this data source will need to be linked (even if only at the group level) to other data from the federal government and beyond. The national-level data collected on a regular basis should complement other sources, both government and nongovernment, for use by researchers. Research data centers operated by the federal statistical agencies can create opportunities for these kinds of coordinated efforts, which must comply with respondent confidentiality and privacy requirements.

Going forward, much of the value of the federal statistical apparatus will depend on whether it can expand its capacity to link data sources—survey and nonsurvey, national and local. The Census Bureau, for one, already has a significant capacity to link data sources; of course, the resulting research data products are stripped of individual identifiers and can typically only be accessed through secure means. Much of this work is being done by researchers using datasets available on a restricted-access basis in the Census Bureau’s Research Data Centers.

Some of the most innovative programs have taken place on the busi-


4Alexander (1998) recommended that, for the ACS, direct (nonmodel-based) annual estimates should be limited to areas with populations of at least 65,000; estimates for areas with smaller size populations can be made by pooling data across years—as small as 15,000 when data from 5 years are used. Because of the need for these smaller area estimates, the Census Bureau has actively supported research on indirect modeling methods.

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