The foundation of a successful census is a complete and accurate address list and the maps that go with it. The Bureau’s MAF is an inventory of the nation’s roughly 120 million living quarters and serves as the basic control for the census in that it is used to deliver questionnaires as well as organize the collection and tabulation of data. The Bureau develops its maps from its TIGER database, which contains such information as housing unit locations, zip codes, streets, geographic borders, census tract and block boundaries, railroads, airports, and schools. The Bureau goes to great lengths to develop a quality address list and maps, working with the U.S. Postal Service; federal agencies; state, local, and tribal governments; local planning organizations; the private sector; and nongovernmental entities. The Bureau also sends thousands of temporary census workers into the field to verify address information on site. For the 2000 Census, the Bureau spent around $390 million on its address list compilation activities, which was about 6 percent of the $6.5 billion spent on the census, or about $3.33 for each housing unit. Despite these efforts, the Bureau has historically encountered difficulties locating the dwellings of migrant farm workers because of a variety of obstacles ranging from workers’ literacy levels to their legal status (see fig. 1). The net result is that migrants’ places of residence may not get included in the MAF, which decreases their chances of being counted in the census. Ensuring that migrant farm workers are included in the census is important for at least two reasons. First, the Bureau is legally required to count all persons who reside in the United States on Census Day, regardless of their citizenship status or whether they are here legally or illegally. Second, according to the Bureau, migrant and seasonal farm workers have unique health, job safety, training, education, and other requirements. Federal, state, and local governments as well as other organizations use census data to plan and fund many of the programs that address these needs. Our objectives were to (1) review the adequacy of the Bureau’s operations for locating migrant farm workers and their dwellings during the 2000 Census, and (2) identify how, if at all, the Bureau can improve those operations for the next decennial census in 2010. Because the Bureau does not keep data on how well its address list development operations located the dwellings of specific population groups such as migrant farm workers (the operations were developed to locate dwellings regardless of who might live in them), to meet our two objectives we examined relevant Bureau program and research documents. We also interviewed key Bureau headquarters officials who were responsible for planning and implementing the address list development operations. Moreover, to obtain a local perspective on how the Bureau implemented its address list development operations and tried to overcome the challenges of locating the dwellings of migrant farm workers, we interviewed Bureau officials from 4 of its 12 regional offices (i.e., Atlanta, Charlotte, Dallas, and Los Angeles). We also interviewed former local census workers in Central California and Florida who helped conduct local address listing. We selected these areas primarily for their geographic dispersion and demographic diversity, and because these areas were identified before the 2000 Census as having a large number of migrant farm workers. Because of the small sample size, the results of our visits cannot be generalized to the Bureau’s MAF-building efforts as a whole, but they do provide useful lessons and innovative practices that the Bureau could consider for 2010. We also included the results of our earlier work that consisted of on-site observations of block canvassing—an operation the Bureau used to verify the accuracy of “city-style” addresses. We made these observations when the operation was underway in the spring of 1999 in Dallas, Tex; Los Angeles, Calif.; Paterson, N.J.; and Long Island, N.Y., which we chose for their geographic and demographic diversity. We also included the results of our survey of a stratified random sample of 250 local census office managers in which we obtained responses from 236 managers (about a 94 percent overall response rate). The survey—which asked local census office managers about the implementation of a number of key field operations—can be generalized to the 511 local census offices located in the 50 states. All reported percentages are estimates based on the sample and are subject to some sampling error as well as nonsampling error. In general, percentage estimates in this report for the entire sample have a sampling error ranging from about +/- 4 to +/- 5 percentage points at the 95 percent confidence interval. In other words, if all local census office managers in our population had been surveyed, the chances are 95 out of 100 that the result obtained would not differ from our sample estimate in the more extreme cases by more than +/- 5 percent. To provide further local context, we interviewed representatives of farm worker and other advocacy groups that worked with the Bureau to develop accurate address lists in Florida, Georgia, and California, as well as representatives of local governments who provided local address information to the Bureau. Moreover, we interviewed growers in Florida to discuss how they worked with the Census Bureau. In addition to these field locations, we performed our audit work at Bureau headquarters in Suitland, Md., as well as in Washington, D.C. We performed our audit work for this report from September 2001 through April 2003, in accordance with generally accepted government auditing standards. We requested comments on a draft of this report from the Secretary of Commerce. On June 2, 2003, the Secretary forwarded the Bureau’s written comments on the draft (see app. I), which we address in the “Agency Comments and Our Evaluation” section of this report. The Bureau used more than a dozen operations to help ensure a complete and accurate address list. Although the operations were designed to locate various types of dwellings, not population groups as a whole, if properly implemented their design appears to have been adequate for identifying the hidden living arrangements in which a number of migrant and seasonal farm workers live. However, the operations were generally not as well suited to overcoming language and other challenges associated with locating these population groups. Moreover, various implementation problems hampered the Bureau’s activities at certain locations. The MAF consists of two types of dwellings: housing units such as single- family homes, apartments, and mobile homes and what the Bureau calls “special places and group quarters.” A special place is an entity with which a group quarter is linked. For example, a university is a special place and a dormitory is a group quarter linked to the university. To build the master address list for the 2000 Census, the Bureau employed over a dozen operations nationwide between 1997 and 2000. Each operation was geared toward locating either housing units or special places, although both address types could be added to the MAF by most of the operations. The Bureau enhanced these “standard” address list development operations with supplemental procedures for use in areas with large migrant farm worker populations that directed Bureau employees to, among other actions, check vehicles for evidence of habitation. Operations aimed at locating and verifying the existence of housing units included, among others: United States Postal Service File Transfer (November 1997), where the Postal Service electronically shared with the Bureau the address lists it uses to deliver mail. The MAF was updated periodically by the Postal Service data between November 1997 and January 2000. Local Update of Census Addresses (May 1998–June 2000), where local and tribal government officials reviewed and updated the Bureau’s address lists and maps. Participating governments could submit their changes in paper or electronic form. Address Listing (July 1998–May 1999), a field operation where census workers traveled the roads in areas with mail delivery systems that are not predominately based on street names and street addresses, identifying housing units and updating census maps as necessary. Block Canvassing (January–July 1999), a field operation where census workers verified the addresses of all the housing units in areas with mail delivery systems that are predominately based on street names and street addresses, and updated census maps as necessary. Update/Leave and Update/Enumerate (March–July 2000), field operations where census workers either distributed a census questionnaire to be returned by mail (update/leave) or, in certain areas, attempted to enumerate the household. The address list would be updated at the same time. Nonresponse Follow-up (April–June 2000), where temporary census workers attempted to enumerate households for which a questionnaire was not returned by mail. Any dwellings not on the workers’ assignment lists were also to be enumerated and possibly added to the MAF. Operations meant to locate primarily special places and group quarters included, among others: Advance Visit and Facility Questionnaire operations (November 1998–March 2000), where temporary census workers personally visited with officials of special places to identify locations and specific dwellings. Special Places Local Update of Census Addresses (December 1999–May 2000), where local government officials reviewed and updated the Bureau’s list of special places. Local Knowledge Update (January–February 2000), where local census office staff reviewed the Bureau’s list of special places and added, deleted, or corrected special place names and addresses as appropriate. If all of these operations failed to find a dwelling, people could still be included in the census through the Be Counted program, which the Bureau developed to enumerate people who believed they did not receive a census questionnaire, or were otherwise not included in the census. The program also allowed people with no usual residence on Census Day such as migrants, seasonal farm workers, and transients to get counted in the census. The Bureau placed Be Counted forms (specially modified short- form questionnaires) in community centers, churches, groceries, and other locations where the targeted groups were thought to congregate (see fig. 2). As shown in figure 3, the MAF-building operations were sequential and took place between 1997 and 2000, which helped ensure that an address missed in one operation could be found in a subsequent operation.