The Bureau has been using this survey, known  as the ACS Supplementary Survey, to test procedures and to produce  annual data for geographic areas with populations of 250,000 or more. According to the plan the Congress approved, the first annual ACS  data for geographic areas with populations larger than 65,000 will be  published beginning in 2006 with data for 2005; 3-year averages for  geographic areas with populations between 20,000 and 65,000 will begin in  2008; and 5-year averages for geographic areas with populations smaller  than 20,000, including Census tracts and block groups, will begin in   2010. For the ACS test program,  the underlying population and housing characteristics varied. The Census Bureau did not  provide a date when the methodology would be incorporated. Although it also has solicited advice from NAS panels, advisory committee  members, and experts at workshops and conferences on some of the  issues we have identified in this report, there is no indication that the  Census Bureau will be following this advice. It has been more than a year since the Census Bureau announced, in  March 2003, that it was looking into establishing an ACS partnership  program that would involve advisory groups and expert panels to help it  improve the program. We found that no such program has been  established yet. When we reviewed the previous plan and  other alternatives to the proposed ACS that would provide more timely  and reliable data for small geographic areas, we determined that the only  viable alternative to the current plans would be to expand the sample size  for 2009–11, as proposed earlier. In addition, the Census Bureau has announced that comparisons of   2000 ACS and 2000 Census long-form data critical to the transition to the  full ACS will be limited. Resolving all issues for the 2008 ACS is critical if  these data are to be fully consistent with the ACS data for 2009–12 and the  2008–12 averages are to be fully consistent with the 2010 Decennial  Census short-form data. Conclusions

The Census Bureau’s development of the ACS goes back several decades  and has included intensive research and field testing programs, as well as  substantial outreach efforts, in particular through the reports and  workshops at NAS. Recommendations for Executive Action

To ensure that the ACS is an adequate replacement for the Decennial  Census long form, we recommend that the Secretary of Commerce direct  the Census Bureau to (1) revise the ACS evaluation and testing plan and  focus on the issues we have identified in this report; (2) provide key  stakeholders, such as the National Academy of Sciences, with meaningful  and timely input on decisions relating to these issues; and (3) make public  the information underlying the Census Bureau’s decisions on these issues  when it makes the decisions. Further delay will undercut the ability of the ACS to provide, by  2010, small-area data of the type traditionally collected on the census long-form sample and  will jeopardize 2010 planning, which currently assumes a short-form-only census.” “the Bureau should also study the effects of imputation on the distributions of  characteristics and the relationships among them and conduct research on improved  imputation methods for use in the American Community Survey (or the 2010 census if it  includes a long-form sample).” “publish distributions of characteristics and item imputation rates, for the 2010 census and  the American Community Survey (when it includes group quarters residents), that  distinguish household residents from the group quarters population (at least the  institutionalized component). Each question provided information  required by statute. These comparisons will have about the same  reliability as changes between two censuses using data collected in the Census long  form.” “encourage analysts to use the same length of cumulation when comparing areas of  different sizes . . . . For example, we would use one year for comparing states, but would  recommend 5 years for all the counties in a table comparing large and small counties.”
Alexander noted that this approach differed from that of Kish, the  developer of the concept of a “rolling sample,” who would “let us use  tables of counties with one-year estimates for large counties, 3-year  averages for medium-sized ones, and 5-year averages for small ones.” He  concluded this section of the paper by saying, “It will be interesting to see  what practices data users will adopt in this regard.” “If there is little change in the population over the time covered by the average, the  interpretation is about the same as that of a point-in-time estimate with the advantage that  the ACS estimate is more current than the historical decennial census long-form  estimate.”
The paper provided examples with “naive” assumptions about how users  extrapolate between censuses to show that multiyear averages “work.” By  implication, under other conditions, users will need guidance on when  multiyear averages can be used.
Why GAO Did This Study

The Congress asked GAO to review operational and programmatic aspects of the Census Bureau's ACS that will affect the reliability of small geographic area data. The ACS will be a mail survey of about 3 million households annually, whose results will be cumulated over 5 years to produce estimates that will replace information previously provided by the Decennial Census long form. In addition, annual data will be published for geographic areas with 65,000+ populations and as 3-year averages for areas with populations of 20,000 to 65,000. Annual data will be published beginning in 2006 with data for 2005. The 5-year averages for 2008-12 will provide data for small geographic areas.

What GAO Found

The Census Bureau's development of the American Community Survey goes back several decades and has included intensive research and field testing programs, as well as substantial outreach efforts, in particular through the reports and workshops at the National Academy of Sciences (NAS). However, if the ACS is to be an adequate replacement for the Decennial Census long form as the major source of data on small geographic areas and if it is to provide similar annual data for larger areas, the Census Bureau will need to incorporate in a timely manner the resolution of issues it has already identified in the ACS testing and 2000 Decennial Census evaluation programs, such as the residence concept, group quarters, and questions on disability; complete the ACS testing plan as originally planned, such as the comparison and evaluation of long form-ACS supplementary survey data at the state level, to identify other unresolved issues and to provide information for users of 2000 Decennial Census long-form data that will be necessary for the transition to the full ACS; evaluate and consult with stakeholders and users on the resolution of issues identified in this report, such as the methodology for deriving population and housing controls, guidance for users on the impact of the characteristics of multiyear averages for small geographic areas, and the presentation of dollar-denominated values; coordinate the results of the testing program for the 2010 Decennial Census short form with the ACS implementation schedule; and resolve all issues so that the ACS estimates beginning with 2008 are consistent with the ACS estimates for 2009-12 and with the 2010 Census short form. Although the Census Bureau has solicited advice from external stakeholders and users and has supported research by its own staff on most of the issues identified in this report, there is no indication that the Census Bureau has yet followed this advice or implemented plans for consultation on resolving these issues. In addition, it has been more than a year since the Census Bureau announced that it was looking into establishing an ACS partnership program that would involve advisory groups and expert panels to improve the program, but no such program has been established. Another issue related to the proposed ACS is how the Census Bureau might provide more timely and reliable small geographic area data. This goal could be accomplished, but it would require additional funding. The most direct approach would be to increase the sample size for 2009-11. This increase would enable the Bureau to provide small geographic area data that would be the replacement for the 2010 Census long form 1 year earlier.