A complete and accurate address list is the cornerstone of a successful census, because it both identifies all households that are to receive a census questionnaire and serves as the control mechanism for following up with households that fail to respond. If the address list is inaccurate, people can be missed, counted more than once, or included in the wrong location. MAF is intended to be a complete and current list of all addresses and locations where people live or could live. The TIGER database is a mapping system that identifies all visible geographic features, such as type and location of streets, housing units, rivers, and railroads. To link these two separate databases, the Bureau assigns every housing unit in the MAF to a specific location in the TIGER, a process called “geocoding.” As shown in figure 1, for the 2000 Census the Bureau’s approach to building complete and accurate address lists and maps consisted of a number of labor- and data-intensive operations that sometimes overlapped and were conducted over several years. This effort included partnerships with the U.S. Postal Service and other federal agencies; state, local, and tribal governments; local planning organizations; the private sector; and nongovernmental entities. The Bureau employed thousands of temporary census workers to walk every street in the country to locate and verify places where people could live. Determining this was no simple task as people can reside in cars, sheds, illegally converted basements and garages, and similar nontraditional and often hidden living arrangements. For the 2000 Census, the Bureau found that the MAF/TIGER databases were less than complete and accurate. Although the number of errors was small in proportion to the total number of housing units at the national level, the errors could be problematic at lower levels of geography for certain purposes for which census data are used, such as allocating federal assistance to state and local governments. According to Bureau evaluations conducted after the 2000 Census, the final census count contained approximately 116 million housing units. However, the address file used to conduct the 2000 Census also contained a number of errors. Bureau evaluations estimate that there were 0.7 million duplicate addresses, 1.6 million vacant housing units misclassified as occupied, 1.4 million housing units not included, 1.3 million housing units improperly deleted, and 5.6 million housing units incorrectly located on census maps. In light of these and other problems, the Bureau made enhancing the MAF/TIGER one of three critical components to support the 2010 Census. The other two components are replacing the long form questionnaire with the American Community Survey and conducting a short-form-only decennial census that is supported by early research and testing. For the 2010 Census, the Bureau is making extensive use of contractors to provide a number of mission-critical functions and technologies. One of the technologies to be provided by a contractor is the MCD. Under a contract awarded on March 30, 2006, a new MCD will be developed for the 2008 Dress Rehearsal. To date, the Bureau has tested two models of the MCD—one during the 2004 Census Test and another during the 2006 Census Test. In January 2005, we reported that the MCD used during the 2004 Census Test to collect nonresponse follow-up data experienced problems transmitting, and the mapping feature was slow. Consistent with our recommendations, the Bureau took steps to improve the dependability of transmissions and correct the speed of the mapping feature. Due to the critical role of contractors to help carry out the 2010 Census, we conducted a review of major acquisitions for the 2010 Census. footnote number should not start a line) In that report issued in May 2006, we highlighted the tight time frames the FDCA contractor has for developing and implementing systems to support the upcoming 2008 Dress Rehearsal and recommended that the Bureau ensure that all systems are fully functional and ready to be assessed in time for the Dress Rehearsal. In addition, on March 1, 2006, we testified on the status of the FDCA project. In that testimony, we discussed the need for the Bureau to validate and approve a baseline set of operational requirements for the FDCA contract, because if not, the FDCA project would be at risk of having changes to requirements, potentially affecting its ambitious development and implementation schedule; implement an effective risk management process that identifies, prioritizes, and tracks project risks; and select detailed performance measures for tracking the contractor’s work. In response to our work, the Bureau stated that they plan to complete these activities as soon as possible. While the Bureau’s MAF/TIGER modernization efforts have progressed in a number of areas, uncertainties and risks remain in dealing with address- related problems that affected the 2000 Census. Currently it is not known whether ongoing research to resolve those problems will be completed in sufficient time to allow the Bureau to develop new methodologies and procedures for improving the MAF by June 2007—the Bureau’s announced deadline for baselining all program requirements. One significant cause for this uncertainty is that some deadlines for completing research do not have firm dates, while other deadlines that have been set continue to slip. In addition, one major research effort using software to identify duplicate addresses (an estimated 1.4 million duplicate addresses were removed during the 2000 Census) did not work any better at identifying true duplicates than what the Bureau already had in place and will not be used in 2010. As a result, duplicate addresses may still be a problem for the 2010 MAF, and to the extent they are not detected, can result in reduced accuracy and increased cost. During the 2000 Census, the Bureau encountered a number of problems with the MAF including (1) missed addresses, where the Bureau failed to include addresses in the MAF; (2) improperly deleted addresses, where the Bureau removed otherwise valid addresses from the MAF; (3) duplicate addresses, with two or more addresses for the same housing unit; and (4) geocoding errors, where addresses were improperly located on a census map. All of the errors affect the quality of census data. When detected, the errors can increase the cost of the census to the extent they result in rework. Moreover, these errors are associated with a variety of living arrangements and addresses, including small, multi-unit dwellings; dormitories, prisons, and other group living facilities, known collectively as “group quarters,” as well as hidden housing units, such as converted basement apartments. As shown in table 1, to address those problems the Bureau has been conducting research and making some operational changes. Although research to find hidden housing units holds promise for a more accurate census, whether the results will be delivered in time to be useful for the 2010 Census is uncertain. While Bureau officials do not have a firm date for completing this research, they do estimate it will be completed by the end of 2006. According to Bureau evaluations, approximately 1.4 million housing units were missed in the 2000 Census. Missed addresses often result when temporary census workers do not recognize that particular structures, such as tool sheds, are being used as residences. Addresses can also be missed when census workers fail to detect hidden housing units, such as basement apartments, within what appear to be single housing units. This is especially true for urban areas, where row houses have been converted into several different apartments. If an address is not in the MAF, its residents are less likely to be included in the census. In May 2003, Bureau staff met with the New York City Planning Department to discuss and observe the address problems associated with small multi-unit structures in Queens, New York. After the visit, the Bureau concluded that delivering questionnaires to small multi-unit structures was a problem that needed to be addressed. In response, the Bureau is using the MAF to identify urban areas, including Baltimore, an area west of Chicago, and counties in New Jersey, where small multi-unit dwellings exist, fitting the description of those that were missed. According to Bureau officials, to accurately identify and count these missed housing units, the Bureau would use update/enumerate procedures—where census workers update the address list and conduct interviews to collect census data—instead of using mailout/mailback procedures, where census forms are mailed to the housing units. Update/enumerate procedures are more labor–intensive and costly than mailout/mailback procedures. In reviewing the research plan on small multi-unit structures,we found no milestones for completing this research. Bureau officials could not provide a firm completion date, but estimated that the research would be completed by the end of 2006. Without clear milestones for completing this research and action plans based on research results, it is uncertain whether the Bureau will have sufficient time to develop a methodology for identifying all the problematic locations across the country where update/enumerate methodology would be necessary and to inform decision makers on the cost of converting these areas from mailout/mailback procedures to update/enumerate procedures. The Bureau has tested new procedures to validate whether an address initially marked “delete” should be removed from the address file. However, the results from that testing, due January 2006, were delayed until April 2006, and were not available at the time of this review. For the 2000 Census, the Bureau found that it had mistakenly deleted 1.3 million existing housing units from the address file used to conduct the census. In some instances, this occurred when the Bureau deleted an address that the U.S. Postal Service had coded as a business address, although people were living at that address. According to a Bureau evaluation, when this happens, the Bureau relies on census workers to find and add back those units. Bureau officials stated that identifying residential housing units is difficult for some structures, such as apartments in businesses. The Bureau would also delete an address if no census form was returned from the unit and if two other census operations determined that the address should be deleted.