Recommendation 4-6: The Census Bureau should conduct experiments to determine the extent to which ACS respondents give different answers to the decennial census usual residence rule and the ACS 2-month residence rule and the extent to which they apply the specific ACS residence rules (for example, reporting commuter workers at the family residence, applying the 2-month rule prospectively). To help clarify residence according to the census and ACS concepts, the experimental questionnaire should ask about other residences at which respondents spend time. The Census Bureau should assess the implications of the experimental results for ACS population estimates for different geographic areas and population groups. Depending on the results, the Census Bureau should consider appropriate changes in the ACS questionnaire instructions on residence or in the residence rules themselves.

Sampling and Data Collection for Group Quarters

Recommendation 4-7: The Census Bureau should discuss with data users their requirements for detailed information from the ACS for residents of institutions and other types of group quarters, particularly at the local level. The discussions should assess benefits against costs, and the results should be used to determine any changes to the group quarters component of the ACS—for example, the possible deletion of institutions from the ACS universe—that would be cost-beneficial for users and stakeholders.

Data Products—Confidentiality Protection

Recommendation 4-8: Because of the potential value of month of data collection for analysis of the ACS public use microdata samples, the Census Bureau should revisit its decision to omit this variable as a confidentiality protection measure. If further research determines that including exact month of data collection would significantly increase disclosure risk, the Census Bureau might consider perturbing the month of data collection or taking other steps to protect confidentiality. Similarly, the Census Bureau should consider developing selected summary tables that identify the season of collection (such as summer or winter) for geographic areas for which such information would be useful.


Recommendation 4-9: The Census Bureau should undertake research to develop confidentiality protection rules and procedures for tabulations from the ACS that recognize the protection afforded to respondents by pooling the data over many months. Whenever possible, the



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