The cost of the census has been escalating over the last several decennials. The 2010 decennial was the costliest U.S. Census in history at about $12.3 billion, and was about 31 percent more costly than the $9.4 billion 2000 Census (in 2020 dollars). The average cost for counting a housing unit increased from about $16 in 1970 to around $92 in 2010 (in 2020 dollars). According to the Bureau, the total estimated cost of the 2020 Census is approximately $12.5 billion dollars (in 2020 dollars). Meanwhile, the return of census questionnaires by mail (the primary mode of data collection) declined over this period from 78 percent in 1970 to 63 percent in 2010 (see figure 1). Declining mail response rates—a key indicator of a cost-effective census—are significant and lead to higher costs. This is because the Bureau sends temporary workers to each non-responding household to obtain census data. As a result, non-response follow-up is the Bureau’s largest and most costly field operation. In many ways, the Bureau has had to invest substantially more resources each decade to match the results of prior enumerations. The 2020 Decennial Census is not the first decennial census to be on GAO’s High- Risk-List. Both the 2000 and the 2010 Decennial Censuses were also high-risk areas. All three of these censuses have had issues related to technology and design changes. Achieving a complete and accurate census is becoming an increasingly daunting task, in part because the nation’s population is growing larger, more diverse, and more reluctant to participate. When the census misses a person who should have been included, it results in an undercount; an overcount occurs when an individual is counted more than once. Such errors are particularly problematic because of their differential impact on various subgroups. Minorities, renters, and children, for example, are more likely to be undercounted by the census. The Bureau faces an additional challenge of locating unconventional and hidden housing units, such as converted basements and attics. For example, as shown in figure 2, what appears to be a small, single-family house could contain an apartment, as suggested by its two doorbells. If an address is not in the Bureau’s address file, its residents are less likely to be included in the census. The Bureau estimated a net undercount of 790,000 housing units in 2010. The basic design of the enumeration—mail out and mail back of the census questionnaire with in-person follow-up for non-respondents—has been in use since 1970. A key lesson learned from 2010 and earlier enumerations is that this “traditional” design is no longer capable of cost- effectively counting the population. In response to its own assessments, our recommendations, and studies by other organizations, the Bureau has fundamentally reexamined its approach for conducting the 2020 Census. Its plan for 2020 includes four broad innovation areas (re- engineered field operations, administrative records, verifying addresses in-office, and the Internet self-response option). The Bureau believes these innovations will save it over $5 billion (2020 dollars) when compared to what it estimates conducting the census with traditional methods would cost. However, in June 2016, we reported that the Bureau’s life-cycle cost estimate of $12.5 billion cost was not reliable and did not adequately account for risk. To help drive these innovations, the Bureau plans to rely on about 50 IT systems that are being developed or are already in production. Eleven of these systems are expected to be provided by an enterprise-wide initiative called Census Enterprise Data Collection and Processing (CEDCaP), which is managed within the Bureau’s IT Directorate. This initiative is a large and complex modernization program intended to deliver a system-of-systems to support all the Bureau’s survey data collection and processing functions, rather than continuing to rely on unique, survey-specific systems with redundant capabilities. According to Bureau officials, the 39 other systems (referred to as non-CEDCaP systems) are to be provided by the 2020 Census Directorate or other Bureau divisions. The four innovation areas the Bureau plans for 2020 show promise for a more cost-effective head count (see table 1). However, they also introduce new risks, in part because they include new procedures and technology that have not been used extensively in earlier decennials, if at all. As a result, it will be imperative that the Bureau conduct a robust testing program culminating in the 2018 End-to-End Test that is to demonstrate the systems and operations that will be used for 2020 under operational conditions. On October 18, 2016, the Bureau decided to stop two field test operations planned for fiscal year 2017 in order to mitigate risks from funding uncertainty. Specifically, the Bureau said it would stop all planned field activity, including local outreach and hiring, at its test sites in Puerto Rico, North and South Dakota, and Washington State. The Bureau is not carrying out the planned field tests of its mail-out strategy and follow up for non-response in Puerto Rico or its door-to-door enumeration. However, the Bureau is continuing with other planned testing in fiscal year 2017, such as tests focusing on systems readiness and Internet response. One of these tests, which began in March 2017, included 28 of the roughly 50 systems to be used in 2020 operations. Further, the Bureau said it would consider incorporating the canceled field activities elements within the 2018 End-to-End Test, which is expected to begin in August 2017. The Bureau maintains that stopping the 2017 Field Test will help prioritize readiness for the 2018 End-to-End Test and mitigate risk. Nevertheless, as we reported in November 2016, it also represents a lost opportunity to test, refine, and integrate operations and systems, and it puts more pressure on the 2018 test to demonstrate that enumeration activities will function as needed for 2020. Administrative records—information already provided to the government as it administers other programs, such as mail collection by the U.S. Postal Service—have been discussed and used for the decennial census since the 1970s, but the Bureau plans a more significant role for them for 2020 to reduce fieldwork and control costs. For example, the Bureau plans to use administrative records to help determine vacant and occupied housing units and thus improve the efficiency of following-up with non-respondents. The Bureau has estimated that using these records could save up to $1.4 billion compared to traditional census methods. In 2015, we found that the Bureau has already demonstrated the feasibility of using administrative records. However, it still faces challenges with using them for the 2020 Census. For example, although the Bureau has no control over the accuracy of data provided to it by other agencies, it is responsible for ensuring that data it uses for the 2020 Census are of sufficient quality for their planned uses. Another challenge we identified is the extent to which the public will accept government agencies sharing personal data for the purposes of the census. Related concerns involve trust in the government and perceptions about burden on respondents as well the social benefits of agencies sharing data. Moreover, in addition to using administrative records to reduce fieldwork, the Bureau is considering several additional opportunities to leverage administrative records to help improve the cost and quality of the 2020 Census. It will be important for the Bureau to set deadlines for deciding which records it will use and for which purposes for those records. In this way, the Bureau can monitor its progress and prioritize which activities—or records—to continue pursuing, or to abandon, if time becomes a constraint. When households do not respond to the census and when the Bureau does not obtain information about the household while knocking on doors during its non-response follow-up operation, the Bureau may have to impute attributes of the household based on the demographic characteristics of surrounding housing units as well as on administrative records. We reported in 2016 that during the Bureau’s 2016 Census Site Test, the Bureau experienced about 20 and 30 percent of its test workload as non-interviews at its two test sites in Harris County, Texas, and Los Angeles County, California, respectively. According to the Bureau, non-interviews are cases where no data or insufficient data are collected, either because enumerators make six attempted visits without success (the maximum number the Bureau allows), or interviews are not completed due to, for example, language barriers or dangerous situations. Identifying root causes of problems is something we look for when determining progress within a high-risk area. Accordingly, while the 2016 Census Test non-interview rate is not necessarily a precursor to the 2020 non-interview rate, because of its relationship to the cost and quality of the census, it will be important for the Bureau to better understand the factors contributing to it. The Bureau is managing the acquisition and development of new and modified IT systems, which adds complexity to the design of the census. We have previously reported that the Bureau has faced challenges in managing internal coordination and governance, contracts, schedule, scope, and costs for its IT systems, and we have ongoing work reviewing each of these challenges: Internal coordination and governance. Different divisions are responsible for acquiring and developing different systems and technology supporting the 2020 Decennial Census. Eleven of the roughly 50 systems planned to be used in the 2018 End-to-End test are being delivered by the Chief Information Officer’s (CIO) IT Directorate through the CEDCaP program, with the other 39 being managed and developed within the 2020 Census Directorate or other Bureau divisions. We have reported the Bureau has had challenges in coordinating and governing between these divisions. In August 2016 we reported that the two programs lacked effective processes for managing their schedule, risk, and requirements interdependencies.We stated that until the two programs establish schedules that are completely aligned, develop an integrated list of all interdependent risks, and finalize processes for managing requirements, both programs are at risk of not delivering their programs as expected.