The decennial census is mandated by the U.S. Constitution and provides data that are vital to the nation. This information is used to apportion the seats of the U.S. House of Representatives; realign the boundaries of the legislative districts of each state; allocate billions of dollars in federal financial assistance; and provide social, demographic, and economic profiles of the nation’s people to guide policy decisions at each level of government. As shown in figure 1, the cost of enumerating each housing unit has escalated from around $16 in 1970 to around $94 in 2010, in constant 2010 dollars (an increase of over 500 percent). At the same time, the mail response rate—a key indicator of a cost-effective enumeration—has declined from 78 percent in 1970 to 63 percent in 2010. In many ways, the Bureau has had to invest substantially more resources each decade just to try and match the results of prior enumerations. Beginning in 1990, we reported that rising costs, difficulties in securing public participation, and other long-standing challenges required a revised census methodology—a view that was shared by other stakeholders. We and other organizations—including the Bureau itself—have stated that fundamental changes to the design, implementation, and management of the census must be made in order to address operational and organizational challenges. Accordingly, in preparation for the 2020 Census, the Bureau has been researching and testing new methods and technologies to more cost- effectively count the population while maintaining high-quality results. This includes conducting several major field tests that are intended to inform the September 2015 preliminary design decision. For example, in 2014 the Bureau tested new methods for conducting self-response and non-response follow-up (referred to as the 2014 Census Test) in the Maryland and Washington, D.C., area. The Bureau is also conducting tests in 2015 that are expected to inform the design decision, including the Address Validation Test, which was completed in early 2015 and was used to examine new methods for updating the Bureau’s address list; the 2015 Census Test, which is currently being conducted in Arizona to test, among other things, reengineered non-response follow-up field operations, as well as enabling enumerators to use their personally owned mobile devices to collect census data; and the Optimizing Self Response Test, which is currently being conducted in Savannah, Georgia, and the surrounding area and is intended to further explore methods of encouraging households to respond using the Internet, such as using advertizing and outreach to motivate respondents, and enabling households to respond without a Bureau-issued identification number. Following its design decision, the Bureau plans to conduct additional research and testing and further refine the design through 2018. By September 2018, the Bureau plans to have fully implemented the design so that it can begin operational readiness testing. Figure 2 provides the timeline for planned 2020 Census research and testing. The Bureau has been making important progress in researching and testing various design options associated with four interrelated cost- savings initiatives: using data previously provided to the government to help enumerate the population, updating the Bureau’s address list and maps of the nation, only where needed, reengineering management of field work, and maximizing self-response. Combined, the Bureau estimates these efforts could generate up to $5 billion in cost savings and that the total life-cycle cost for the 2020 Census will be approximately $12.7 billion. However, we have identified various challenges and unanswered questions in these areas that, if unresolved, could affect the accuracy of the count and put the estimated cost savings at risk. The Bureau has identified or acknowledged many of these issues and is working to address them. The Bureau incurs a large part of the census’ cost while following up at residences that did not return a census questionnaire. To ensure a complete count, Bureau guidance in 2010 had enumerators visit some places up to six times to try to obtain a response. In addition to being costly, such follow-up can also affect the accuracy of the count, because when census enumerators cannot contact a household, they may turn to a neighbor or some other person knowledgeable about the household to obtain the data. However, this information may be less reliable than information provided by a household member. In addition, many residences are subsequently found to be vacant or nonexistent. For example, in one operation in 2010 with the purpose of verifying whether some housing units were vacant or should be deleted from the Bureau’s address list, the Bureau visited nearly 9 million housing units at a cost of about $280 million in labor and other expenses. To reduce the need for these costly operations and to increase accuracy, the Bureau is testing how it might be able to expand its use of information the government already has from the administration of other programs— administrative records. The Bureau is conducting these tests in Maricopa County, Arizona, this month and has further testing planned for 2016. Examples of administrative records include Social Security Administration data and Medicare records, as well as records from state, local, and tribal governments and commercial sources. The Bureau has previously made limited use of administrative records. For example, it used U.S. Postal Service files to update its address list. The Bureau estimates that using administrative records for the 2020 Census to reduce the number of in- person visits, local census offices, and operations needed has the potential to save $1.2 billion. Our ongoing work and our December 2010 reportBureau will need to resolve a number of questions before it will be able to realize cost savings or improvements in data reliability from the use of such records, including the following: What records will meet the Bureau’s needs? The Bureau is exploring questions about the quality of other records and their completeness. Information contained in those records was collected for other purposes, so it may not always provide exactly what the Bureau needs. For example, while race and ethnicity data are collected in the census, the records available to the Bureau may not record this information. Likewise, while the Bureau needs the location of a residence for apportionment and other purposes, available records may only provide locations where people receive mail such as a post office box. To what extent does the Bureau have access to these records for operational purposes? Some of the data the Bureau may want to use is personally identifiable information collected for other specific purposes. In some cases, the Bureau may need to enter into agreements with other agencies or levels of government to obtain access. In other cases, legislative changes may be needed to provide the Bureau with the necessary access authority. The Bureau will need to be sensitive to the time involved for these efforts so that it has the access it may need in time for 2020. To what extent will the public accept the sharing of personal data across government agencies for purposes of the census? The Bureau and others have ongoing research exploring public perceptions on topics such as trust, the potential for decreased burden on respondents, and the social benefits of sharing data. This research is also exploring the factors relating to public outreach that the Bureau may need to focus on in order to enhance the public’s acceptance of greater use of administrative records. We have ongoing work examining the Bureau’s efforts to research the use of administrative records for the 2020 Census, including the test in Maricopa County, Arizona. We anticipate issuing the results this fall. The Bureau relies on a complete and accurate address list to identify all households that are to receive a census questionnaire. The address list also serves as the control mechanism for following up with non- responding households. Accurate addresses and precise maps are critical for counting the population in the proper locations—the basis of congressional reapportionment, redistricting, and allocations of federal aid to state and local governments. In prior decades the Bureau employed field staff to walk almost every street in the nation as one of several operations to update the Bureau’s inventory of addresses and geography—in 2013, we testified that the Bureau’s 2010 address canvassing operation required 140,000 temporary workers to verify 145 million addresses at a cost of $444 million. The Bureau has relied on this operation to help identify hidden housing units—that is, people living in, for example, converted basements or lofts—as well as changes to the address list such as from newly constructed or demolished residences. To reduce the scope of this operation, the Bureau is focusing on areas that it believes have experienced change, such as rapid recent housing development, and for which the Bureau has no data sources capturing those changes. The Bureau is working with the U.S. Postal Service, other federal agencies, and state, local, and tribal governments on an initiative that allows government agencies at all levels to regularly share and continuously update their address lists and road data with the Bureau. To help fill in gaps and better target reduced resources, in January 2015 the Bureau solicited information from commercial firms on their capabilities to detect changes in addresses in local areas. Additionally, in February 2015 the Bureau solicited commercial proposals to provide national address or imagery datasets. The Bureau recently completed tests of some modeling methods to help identify where updates are most needed, and has additional tests planned for 2016. The Bureau estimates it will save up to $1 billion with the successful implementation of this initiative. Going forward, the Bureau’s success at more efficiently updating its address list and maps depends on how it resolves questions such as the following: Which map and address data sources are the most cost- effective? In October 2014, we found that the Bureau needed to implement processes for reviewing the cost and quality of data source selections and for documenting support for those decisions while documenting management approval of key data source decisions. The Bureau agreed with our corrective recommendations and is taking steps to address them. The Bureau has ongoing research to determine how best to measure cost and quality trade-offs in data sources. Will the Bureau be able to complete a nationwide continuous update of its addresses and maps in time for 2020? With over 3,200 counties in the country, in addition to other local and state governments the Bureau might be partnering with, the Bureau has much work to do.