To help ensure accuracy in the population count in 2000, the Bureau used  telephone interviews in another operation to follow up with two types of  household responses: households too large to include all their members on  the form and households with apparent discrepancies on their  questionnaires, such as when the number of people reported in the  household population box does not match the number of people whose  name and demographic information is included on the form. The Bureau completed FV at a cost of $21 million, 38 percent lower than  the $33.8 million estimated for the operation. The Bureau completed CFU at an estimated cost of $267 million, about 2  percent less than the initial cost estimate for the operation. Given mandated deadlines that the Bureau faces for delivering census  tabulations, completing field data collection including CFU and FV on  schedule was crucial for subsequent processing activities to proceed and  be completed on schedule. The Bureau’s Increase in the Number and Types of CFU Cases Should Improve Overall Census Accuracy

A key design decision the Bureau made for the 2010 CFU was to expand  the scope of its coverage follow-up operation from 2000 to follow up on  additional types of cases that it believed would help reduce the differential  undercount. According to the Bureau, the 2010 CFU operation  should result in more than 2.9 million coverage errors being removed from  the census, including overcounts and undercounts, compared to more than  400,000 coverage errors being removed in 2000. The more coverage errors  are removed from the official census count, the more the overall accuracy  of the census is improved. The Effect of the Bureau’s Prioritization of Coverage Follow-up on Differential Undercounts Is Not Clear

A second key design decision the Bureau made for CFU was to prioritize  the types of cases it would follow up on, likely increasing the overall  number of coverage errors corrected but possibly affecting demographic  groups differently. The Bureau’s decisions to expand the scope of CFU and prioritize the CFU  cases will likely result in a greater number of coverage errors being  removed from official census tabulations than were removed in 2000,  increasing CFU’s effectiveness in improving overall census accuracy in  2010. Prioritization of the CFU cases to contact was a reasonable attempt  to leverage the resources and time available for the operation. Furthermore, trends regarding the use of wireless telephones indicate that  some households within hard-to-count populations may be harder to  contact in the future using landline telephone operations. Also, better knowledge of  how best to reach different groups could help identify effective sources of  contact information or strategies for using them for future censuses,  further helping to control costs while still working to address differential  undercounts. Recommendations for Executive Action

We recommend that the Secretary of Commerce require the Director of  the U.S. Census Bureau to take the following three actions to improve the  Bureau’s planning for the 2020 Census:    To help the Bureau decide which coverage probes, if any, to use and  prioritize for future follow-up efforts, assess the extent to which  historically overcounted and undercounted demographic groups  responded to the probes the Bureau followed up on and determine the  effectiveness of specific probes in reducing differential undercounts. To support the Bureau’s efforts to control costs while improving  census accuracy, determine the demographic characteristics of the  households for which it did and did not obtain telephone numbers and,  to the extent feasible, assess the degree to which the telephone  numbers were usable and led to completed contacts for households of  various follow-up groups and demographic characteristics. To ensure that the design of future follow-up efforts is effective in  improving census coverage, assess the implications that trends in  landline and wireless usage and other modes of communication and  new technology may have both on the design decisions for future CFU- like operations and on their effectiveness in improving census  coverage in terms of both overall census accuracy and differential  undercounts. Agency Comments and Our Evaluation

The Secretary of Commerce provided written comments on a draft of this  report on December 1, 2010.
Why GAO Did This Study

The U.S. Census Bureau (Bureau) puts forth tremendous effort to conduct a complete and accurate count of the nation's population and housing; yet some degree of error in the form of persons missed, duplicated, or counted in the wrong place is inevitable due to the complexity in counting a large and diverse population. The Bureau designed two operations, Coverage Follow-up (CFU) and Field Verification (FV), to reduce certain types of counting, or coverage, errors in the 2010 Census. GAO was asked to assess (1) the extent to which the Bureau completed CFU and FV on schedule and within estimated cost and (2) the implications of their key design elements for improving coverage. GAO reviewed Bureau evaluations, planning, and other documents on CFU and FV, and prior GAO work, and interviewed Bureau officials.

What GAO Found

The Bureau completed CFU and FV on schedule and within budget. FV cost $21 million (about 38 percent less than estimated) and CFU cost about $267 million (about 2 percent less than estimated). These operations followed up on potential errors on census returns or lists of addresses after census data had been initially collected. Their completion provided follow-up data used by subsequent data processing that removed errors from the official census tabulations. Three of the Bureau's key CFU design elements will likely improve overall census accuracy, but their effect on undercounts of different demographic groups is not clear. One key design element increased the number and types of follow-up cases. The Bureau expanded the scope of CFU from about 2 million households in the 2000 Census to more than 7 million in 2010. It also added 20 different types of households for potential follow-up. New types included households that reported members temporarily residing elsewhere, such as at college, in nursing homes, or in jail. According to the Bureau, the 2010 CFU operation should remove more than 2.7 million coverage errors from the census. Another key design element of CFU prioritized follow-up cases based on their likelihood to result in a census correction, which was a reasonable attempt to leverage the resources for the operation. However, the Bureau's evaluation plans, based on considerations of what may best reduce cost or increase accuracy in the future, do not link the demographic characteristics of households to how they responded to the additional questions or CFU results for those households. Therefore, it is unclear whether the prioritized follow-up will help reduce differences in the accuracy of census counts across demographic groups. Finally, CFU's design relied on a telephone-only approach to complete follow-up rather than personal visits. This limited costs, resulting in more follow-up and likely more coverage errors being removed from the census. But the telephone-only decision excluded about 700,000 households from CFU that could not be contacted by telephone. Prior Bureau experience indicates that some historically undercounted groups were less likely to be reachable by telephone, and more recent independent research suggests that trends in telecommunication usage may also make it harder to reach some demographic groups this way in the future. Yet the Bureau's evaluation plans do not include an assessment of either the usefulness of the telephone numbers it collected in reaching specific groups or the effect of these trends. Greater understanding of how best to reach different groups as well as the influence of trends on the effectiveness of CFU could help to control costs while working to further reduce differential undercounts.

What GAO Recommends

GAO recommends that the Secretary of Commerce direct the Bureau to assess (1) how well questions to help identify miscounted people on census forms helped reduce differences in the undercounts between demographic groups; (2) the degree to which telephone numbers led to completed contacts for households of various demographic characteristics; and (3) how trends in telecommunication usage and new technology may influence the effectiveness of CFU. The Secretary of Commerce concurred with our recommendations.