2020 Census: Changes Planned to Improve Data Quality

The decennial census produces data vital to the nation. The data are used for congressional apportionment and redistricting; to allocate billions each year in federal funds; and to provide a social, demographic, and economic profile of the nation to guide policy decisions at all levels of government.

Given census data's importance, it is incumbent upon the Bureau to ensure their quality. If people are counted in the wrong place, some states and localities may unduly lose or gain political power through apportionment and redistricting disproportionate to their actual population. Poor outcomes can also result if some households are over counted due to multiple responses, not counted due to missing responses, or miscounted due to incomplete or conflicting responses.

GAO was asked to describe the Bureau's plans for the 2020 Census to resolve multiple, missing, incomplete, and conflicting responses. This report describes how, for 2020, the Bureau plans to (1) determine where to count people, including those in complex living situations, and how this differs from 2010; and (2) resolve multiple, missing, incomplete, and conflicting responses after data collection, and how this differs from 2010. GAO reviewed relevant Bureau documents and interviewed officials responsible for the 2020 Census.

GAO provided a draft of this report to the Bureau. The Bureau provided technical comments, which were incorporated as appropriate.

To determine where people should be counted during each decennial census, the Census Bureau (Bureau) has established residence criteria (see figure). For most people, applying these criteria is straightforward. For others who may be more mobile, like members of the military, college students, migrant farm workers, and people living in group quarters such as federal detention centers or in-patient hospice facilities, it can be more complicated. Therefore, for each decennial the Bureau issues guidance describing how the criteria should be applied to certain complex living situations. For the 2020 Census, the Bureau has updated its guidance on where to count people in six complex living situations, such as U.S. employees deployed overseas. The Bureau plans to count people in other living situations in the same manner as it did in 2010. As in 2010, the Bureau will count prisoners at the correctional facility where they are housed, but also plans to make other resources available to states that want to use prisoners' in-state, pre-incarceration addresses for redistricting purposes instead of their prison addresses.

To resolve multiple responses for a single address, for 2020 the Bureau plans to use a longstanding automated routine—its Primary Selection Algorithm—to determine who to count at the address. For 2020, Bureau documents indicate it updated the algorithm after reviewing various response scenarios and data from past censuses and tests.

To resolve missing household responses following data collection, as it did in 2010, the Bureau plans to use for 2020 a technique it refers to as count imputation, which draws data from similar nearby households to determine whether a housing unit exists, whether it is occupied, and, if so, by how many people. However, for 2020, the Bureau will also try to reduce the number of households which otherwise would have required count imputation and help reduce follow-up field work by drawing on relevant data from administrative records of sufficient quality in conjunction with its non-response follow-up field work.

To resolve incomplete and conflicting information within a household response, the Bureau plans to use a technique it refers to as edit and characteristic imputation. This technique involves drawing data from the same household response, prior census and other administrative records or similar nearby households, which the Bureau believes will improve data quality and produce more accurate results.

The decennial census is constitutionally mandated and produces data  vital to the nation. The data are used to apportion the seats of the U.S.  House of Representatives; realign the boundaries of the legislative  districts of each state; allocate hundreds of billions of dollars each year in  federal financial assistance; and provide a social, demographic, and  economic profile of the nation’s people to guide policy decisions at each  level of government. Furthermore, businesses, nonprofit organizations,  universities, and others regularly rely on census data to support their  work.

Given the importance of census data to the nation, it is incumbent upon  the Census Bureau (Bureau) to count people once, only once, and in the  right place. For example, if people are counted in the wrong place—that  is, away from where they live and sleep most of the time—some states  and localities may unduly lose or gain political power through  apportionment and redistricting that inaccurately reflects their proportion  of the population. Similarly, they may unduly lose or gain key benefits  through improperly distributed federal funds or poorly informed policies.  Inappropriate outcomes can also result if some household residents are  counted more than once due to multiple census responses for the same  address or if they are not counted at all due to missing responses. Further  data quality issues may arise if answers within a household response are  left incomplete or conflict with one another, resulting in missing or  erroneous characteristics—such as age, sex, race, and ethnicity—which  are key to informing public policy and other decisions of importance to our  nation.

Leading up to each decennial census, the Bureau determines how it will  ensure that people are counted in the right place and that multiple,  missing, incomplete, and conflicting responses are resolved. These  determinations are informed in part by the Bureau’s review of how well  this was done during the prior decennial, societal changes during the  intervening years that merit an updated approach, and internal and  external stakeholder input regarding needed changes.

You asked us to describe the Bureau’s plans for the 2020 Census to  resolve multiple, missing, incomplete, and conflicting responses. This  report describes how, for the 2020 Census, the Bureau (1) plans to  determine where to count people, including those in complex living  situations, and how these plans differ from those for the 2010 Census;  and (2) plans to resolve multiple, missing, incomplete, and conflicting  responses following data collection and how these plans differ from those  for the 2010 Census.

To address our objectives, we reviewed Bureau planning, operational,  evaluation, and assessment documents related to the Bureau’s efforts to  enumerate the population for the 2020 Census and prior decennials. We  also interviewed Bureau officials responsible for planning and executing  the 2020 Census and with experience in prior decennials about planned  changes from the 2010 Census.

To describe the Bureau’s plans for determining where to count people for  the 2020 Census, we reviewed Bureau documentation and Federal  Register publications related to 2020 Census residence criteria and  residence situations. We also reviewed Bureau evaluations and  assessments of the 2010 Census which identified concerns related to  counting certain populations. We interviewed Bureau officials responsible  for developing and overseeing the implementation of 2020 Census  residence criteria and residence situations. To understand changes from  2010, we compared the 2010 Census residence criteria and residence  situations to the 2020 Census residence criteria and residence situations  and interviewed Bureau officials to discuss their rationale for these  changes.

To describe the Bureau’s plans for resolving multiple, missing,  incomplete, and conflicting responses following data collection for the  2020 Census, we reviewed and summarized Bureau documentation of  how data are processed after they are collected, including program  management briefings and memorandums, internal process flow  diagrams, internal and external presentations related to post processing,  and documents describing relevant system coding for data processing.  We also interviewed Bureau officials responsible for developing,  administering, and overseeing the internal processing of response data  following collection. To understand changes from 2010, we compared the  2010 Census internal processes to those planned for 2020 and we  interviewed Bureau officials to discuss the rationale for these changes.

We conducted this performance audit from June to December 2019 in  accordance with generally accepted government auditing standards.  Those standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives.

The Bureau is charged with counting every person in the decennial  census once, only once, and in the right place. To ensure fairness and  consistency in where people are counted, for the first decennial in 1790,  Congress established the concept of counting people where they usually  reside. The Bureau has relied on that concept ever since.

Building on the concept of usual residence, the Bureau subsequently  established criteria, which it refers to as residence criteria, to determine  where people should be counted during each decennial (see text box).

Residence criteria  1.  Count people at their usual residence, which is the place where they live and sleep  most of the time.  2.  People in certain types of group facilities on Census Day are counted at the group  facility.  3.  People who do not have a usual residence, or who cannot determine a usual  residence, are counted where they are on Census Day.

For most people, applying the concept of usual residence and the  Bureau’s associated residence criteria is straightforward. For others who  may be more mobile, like members of the military, college students,  migrant farm workers, and people living in group quarters, determining  where to count them can be more complicated. Therefore, for each  decennial the Bureau issues guidance describing how the criteria should  be applied to certain complex living situations for which people commonly  request clarification. The guidance is intended to inform the public about  how to respond and to assist enumerators and other Bureau staff in  administering a proper count.

In addition to counting the nation’s population accurately, the Bureau  must complete the count and tabulate it against a backdrop of immutable  deadlines. The Bureau is required by law to count the population as of  April 1, 2020 (Census Day); deliver state apportionment counts to the  President by December 31, 2020; and provide redistricting data to the  states by April 1, 2021. To meet these deadlines and ensure an accurate  count, the Bureau carries out thousands of interrelated activities before,  during, and after data collection (see figure 1 for a timeline of selected  key activities).

The Bureau Has Refined its Residence Guidance to Help Ensure More People Are Counted in the Right Place

The Bureau Has Updated Its Guidance on Where to Count People in Six Complex Living Situations

The Bureau plans to use its concept of usual residence and its associated  residence criteria to determine where to count people in the 2020 Census  generally as it did in 2010, but in 2018 the Bureau updated its guidance  on how to apply that concept to count people in six complex living  situations (see figure 2 for an overview of these changes). In developing  the guidance for 2020, the Bureau sought input from external  stakeholders on needed changes and solicited public comments on the  draft guidance through the Federal Register. In response, the Bureau  received input and comments from a variety of entities including federal,  state, local, and tribal governments, as well as civil rights and other  advocacy organizations.

Military and civilian employees of the United States deployed  overseas. In 2010, overseas military and civilian employees of the United  States who were U.S. citizens were counted at their home state of record  for apportionment purposes only. For 2020, the Bureau decided to count  these personnel differently depending on whether their permanent duty  station was in the United States. Personnel assigned or stationed  overseas will continue to be counted as they were in 2010. Personnel  stationed in the United States while deployed overseas, however, will  instead be counted at their usual home address in the United States for  both apportionment and redistricting purposes. According to Bureau  documentation, this change resulted from Bureau analysis of data from  the Department of Defense which found that personnel deployed  overseas were there for shorter periods and were likely to return to their  prior usual place of residence, whereas personnel assigned or stationed  overseas generally remained overseas for greater periods and often did  not return to their prior stateside location.

Military and civilian employees of the United States deployed,  stationed, or assigned overseas who are legal U.S. residents but not  citizens. For 2020, the Bureau plans to count this population the same  way it counts U.S. citizens working for the federal government overseas,  as described above. According to a Bureau assessment of how it counted  personnel overseas in 2010, its guidance for federal agencies that  provide the Bureau with data on overseas personnel was unclear on the  treatment of non-citizens. According to Bureau officials, it is therefore  likely that other federal agencies following that guidance generally  excluded non-citizens from the 2010 count. Based on the Bureau’s  assessment, the Bureau plans to make clear in its 2020 guidance that  U.S.-resident non-citizens working for the federal government overseas  are to be counted the same way as U.S. citizens. Bureau officials stated  that this change should ensure that U.S.-resident non-citizens are  counted more consistently with other U.S. residents.

Crews of U.S. maritime and merchant vessels sailing between a U.S.  and a foreign port. In 2010, if a U.S. maritime or merchant vessel was  sailing between a U.S. and a foreign port on Census Day, then the  crewmembers were not counted. For 2020, the Bureau plans to count  these crewmembers at their onshore usual residence in the United States  or, if they have none, then at the vessel’s U.S. port of departure or arrival.  This matches how the Bureau counts crewmembers if their vessel is at a  U.S. port or sailing between two U.S. ports. According to Bureau  documentation, this change resulted from Bureau analysis and  consultation with stakeholders (including the Maritime Administration)  which found that crewmembers in each of these situations usually retain  an onshore residence in the United States where they live and sleep most  of the time so they should be counted in the same way.

Juveniles in non-correctional residential treatment centers. For 2020,  the Bureau plans to count this population at the U.S. residence where  they live and sleep most of the time or, if they have no usual home  address, then at the facility. In 2010, they were counted at the facility. The  Bureau made this change after concluding that these juveniles typically  only stay at residential treatment center facilities temporarily and  generally have a usual home elsewhere to which they return after  treatment is completed.

Religious group quarters residents. For the 2020 Census, the Bureau  will count this population at the religious group quarters facility. In 2010,  this population was counted at their usual home address or, if they had no  usual home address, then at the facility. The Bureau made this change  after concluding that this population typically does not have a place of  usual residence elsewhere.

According to Bureau officials, the Bureau expects the updated guidance  will provide greater clarity and result in more informed responses and,  thus, higher quality data. Among other things, Bureau officials stated that  the data will more accurately reflect the composition of local communities.

The Bureau Will Continue to Count People in Other Living Situations as It Did in 2010

For the 2020 Census, the Bureau did not change its guidance regarding  where to count people in other complex living situations. For example, the  Bureau did not make changes to where it will count college students, who  will continue to be counted at their parents’ or guardians’ home if they live  and sleep there most of the time or, if they live away from their parents’ or  guardians’ home, then at their on- or off-campus residence. See table 1  for an overview of where the Bureau will count people in complex living  situations the same as it did in 2010.

In addition, the Bureau’s guidance includes examples of situations in  which people should not be counted in the census, such as the following: people living outside the United States on Census Day who are not  military or civilian employees of the U.S. government and are not  dependents living with military or civilian employees of the U.S.  government; babies born after Census Day or people who die before Census Day;  college students living at and attending college outside the United  States; and  citizens of foreign countries visiting the United States, such as on  vacation or a business trip.

To help census respondents understand who and where to count  household members and others, the Bureau is translating key terms from  its census form for 2020 into 59 languages and making it available to  community partners and others who may be in a position to help  linguistically isolated groups provide accurate responses. It is translating  scripted responses to questions about complex living situations into 12  foreign languages to be used by staff who will help answer questions  about and take responses over the telephone.

The Bureau Will Continue to Count Prisoners at the Correctional Facility but Plans to Offer States Supplemental Tools for Redistricting with Prisoners’ Pre- Incarceration Addresses

The Bureau reports that stakeholder feedback on where to count  prisoners largely urged the Bureau to count them at their pre- incarceration addresses to avoid shifting political power to the prison  locations at the expense of the prisoners’ home communities. However,  the Bureau concluded that counting prisoners anywhere other than the  correctional facility would be less consistent with the concept of usual  residence, since the majority of people in prisons live and sleep there  most of the time. Therefore, for 2020, the Bureau decided that it will  continue to count prisoners at the correctional facility as it did in 2010.  However, the Bureau will make available to states two tools to allow them  to “move” their prisoner population to the prisoners’ pre-incarceration  addresses for redistricting purposes. The tools are intended to support  such movement within but not across state boundaries.

The Bureau is providing states with an online tool that will identify the  census geographical block that the population would be tabulated in  for any state-provided addresses. If a state wants to “move” the  tabulation of specific prisoners within its boundaries, this information  will let state officials know which block tabulations to adjust. On  November 4, 2019, the Bureau launched the web page that will  support states in using this tool. The Bureau plans to update it with  2020 Census geographic data in February 2021, before the Bureau is  required to provide redistricting data to the states.

The Bureau also plans to provide states with data on group quarters,  which will contain a separate count of their prisoner populations, as  part of each state’s redistricting file. By including group quarters data  in the redistricting file, the Bureau plans to provide these group  quarters data to users 1 to 2 months earlier than it did in 2010 when it  provided group quarters data separately from the redistricting file.  According to the Bureau, this earlier release will benefit many users,  including state officials who must consider whether to include or  exclude certain populations when redrawing boundaries as a result of  state legislation.

The Bureau Is Planning Additional Changes to Improve Count Accuracy, Completeness, and Consistency Following Data Collection

Once the Bureau has completed its decennial data collection efforts, it  generally finds that a small proportion of responses have data quality  issues that were not resolved during preceding operations. In these  cases, (1) some addresses have multiple responses, (2) some  households are missing responses altogether, or (3) some responses  include answers that are incomplete or conflict with one another. The  Bureau has a variety of plans to resolve these issues (see figure 3).

Determining Whom to Count at Addresses with Multiple Responses

The Bureau may receive multiple census responses from a household for  various reasons. For example, different members of the same household  could each respond by mail or over the internet, or one member could  mail a response and another answer a census worker’s questions in  person during the Bureau’s non-response follow-up operation. The  Bureau assessed its response processing in 2010, and identified about  14 million responses for households that already had another response  (roughly 10 percent of the total number of households included in the final  2010 count). The widespread option to respond over the internet is new  for 2020, and while having included it in multiple census tests, Bureau  officials have not set expectations on the extent to which it may increase  the number of addresses at which it gets multiple responses.

To guard against overcounting, as it has in prior decennials, for 2020 the  Bureau plans to use an automated routine—referred to as the Primary  Selection Algorithm—to determine whom to count at addresses for which  it has received multiple responses once data collection is complete.  According to Bureau officials, in making this determination, the algorithm  takes into account a wide range of information, including results from its  fraud detection efforts. We did not examine the algorithm for this review.  In addition, to help ensure the integrity of these determinations, the  Bureau does not disclose the details of the algorithm publicly and permits  only Bureau officials with an operational need to know to access the  algorithm. According to Bureau documentation, the Bureau has updated  the algorithm for 2020 based on its review of various response scenarios  and data from past censuses and census tests.

When the Bureau, after its data collection efforts are completed, has been  unable to reach anyone able and willing to respond at a particular  address or to obtain information about the address and its potential  occupants in other ways—such as through neighbors or a building  manager—it may be left not knowing whether a housing unit even exists  at the address or whether it is occupied, and, if so, by how many people.  As it did in 2010, for 2020 the Bureau plans to use a statistical technique  it refers to as count imputation to fill in missing data about the existence  and number of people living at an address in question. Count imputation  has three types.

Residence status. This is used when the Bureau does not know  whether an address is a real and livable residence. In contrast, it  could be a business or in such disrepair that no one could live there.

Occupancy status. This is used when the Bureau knows that an  address is a real housing unit, but not whether it is vacant or  occupied.

Household size. This is used when the Bureau knows an address is  a real, occupied home, but not how many people live there.

To carry out each of these types of count imputation, the Bureau uses a  technique referred to as hot-deck imputation which employs continually  updated census data from similar nearby households as the basis for  filling in the missing statuses and household size. The Bureau has been  using some form of hot-deck imputation since at least the 1960 Census.

According to Bureau reporting, in 2010, about 500,000 of 137 million  addresses counted in the decennial (0.4 percent) were missing an entire  response and the Bureau therefore used count imputation to determine a  combination of their residence and occupancy status and household  size. The Bureau’s count imputation in 2010 added about 1.2 million  people to the final census count. For 2020, however, some of the missing  responses which otherwise would have required count imputation will  instead be resolved through the use of administrative records in  conjunction with the Bureau’s door-to-door non-response follow-up effort.  Specifically, the Bureau plans to draw on relevant data from records of  sufficient quality thereby reducing the amount of follow-up field work  needed and the number of households in need of count imputation.  According to Bureau officials, they plan to finalize a decision  memorandum in December 2019 specifying the Bureau’s thresholds for  determining whether administrative records are of sufficient quality for  such uses.

According to Bureau officials, tests and evaluations performed during the  preceding decade demonstrate that these uses of administrative records  will provide more accurate results than traditional methods of seeking  information about the address from neighbors and others or from count  imputation alone. Bureau testing and evaluation also identified  improvements to its count imputation technique for 2020, including  enhanced use of administrative records in its hot-deck imputation, which it  expects will generate results better aligned with actual data for those  addresses where it had been missing.

Resolving Incomplete and Conflicting Answers within a Household Response

Once the Bureau has determined the total number of households and  people as of Census Day for apportionment purposes, it resolves  incomplete and conflicting information within individual household  responses for redistricting and final tabulation purposes. Specifically, for  2020, the Bureau plans to ensure that each household response includes  complete and consistent information regarding, for occupied housing  units, the age, date of birth, sex, race, and ethnicity (Hispanic or non- Hispanic origin) of each household resident; their relationship to the  householder; whether the housing unit is rented or owned by a member  of the household; for group quarters, the type of such quarters, such as  federal detention center or in-patient hospice facility; and, if the unit is  vacant, why (see figure 4).

These characteristics (which the Bureau refers to as person and housing  characteristics) may be incomplete or conflicting for various reasons,  including intentional or accidental omissions or errors by the person filling  out the form. According to Bureau data, in 2010, responses for 13 percent  of the people counted in the decennial (about 40 million of the about 300  million counted) contained incomplete or conflicting person characteristics  that the Bureau had to resolve.

For 2020, as it did for 2010, the Bureau plans to use a technique it refers  to as edit and characteristic imputation to fill in incomplete and reconcile  conflicting information in individual household responses. As summarized  in table 2 and described below, it does so using one of three methods,  depending on which characteristics are incomplete or conflicting and on  what other information the Bureau has about those characteristics. The  Bureau has been using some form of characteristic imputation since at  least the 1940 Census.

Use existing information about same person or household. This  method is used when some, but not all, person and household  characteristics are incomplete or conflicting and those characteristics  can be filled in or reconciled using other information about the same  person or household reported within the 2020 response or in prior  census or other administrative records. For example, if a person’s  date of birth is reported but not his or her age, the Bureau will fill in the  age based on the date of birth. If neither age nor date of birth is  reported, the Bureau will look to the 2010 Census to fill in both  characteristics, adjusting for the intervening years.

Use existing information about other people or households. As  with the prior method, this method is used when some, but not all,  person and household characteristics are incomplete or conflicting.  However, unlike the prior method, the incomplete or conflicting  characteristics cannot be filled in or reconciled using other information  about the same person or household reported within the 2020  response or in prior census or other administrative records. Therefore,  the Bureau will look instead to information about other people  included in the same 2020 response or to nearby people or  households from other 2020 responses.

For example, if race is reported for a parent but not a child, the  Bureau will fill in the child’s race using the race provided for the  parent. If there is no information within the household response that  can be used to fill in the child’s race, the Bureau will use a hot-deck  imputation method. As discussed earlier, this method employs  continually updated census data from similar nearby households as  the basis for filling in the needed information.

Use existing information about same or other households. This  method is used when all person characteristics are incomplete. In this  instance, the Bureau will first look to prior census and other  administrative records. If the household size reflected in those records  matches the household size reflected in the 2020 response, the  Bureau will use those records to fill in all person characteristics  available in previous census and administrative records. Remaining  characteristics not filled in by previous census and other  administrative records will be filled in using the methods discussed  above. If the household size totals do not match, the Bureau will use a  hot-deck imputation method, drawing the missing information from  continually updated census data from similar nearby households.

As with other areas of the 2020 Census, the key change in the Bureau’s  plan for resolving incomplete and conflicting information is the enhanced  use of prior census and other administrative records. Specifically, in 2010  the Bureau relied on such records to fill in only race and ethnicity. In  contrast, as discussed above, for 2020 the Bureau plans to use prior  census and other administrative records as an integral part of its edit and  characteristic imputation methods. The Bureau believes this will result in  improved data quality and more accurate results.

We provided a copy of this draft report to the Department of Commerce.  The Census Bureau provided technical comments, which we incorporated  as appropriate.

We are sending copies of this report to the Secretary of Commerce, the  Director of the U.S. Census Bureau, and the appropriate congressional  committees. In addition, the report is available at no charge on the GAO  website at http://www.gao.gov.

If you or your staff have any questions about this report please contact  me at (202) 512-2757 or goldenkoff@gao.gov. Contact points for our  Offices of Congressional Relations and Public Affairs may be found on  the last page of this report. GAO staff who made key contributions to this  report are listed in appendix I.

Appendix I: GAO Contact and Staff Acknowledgments

In addition to the contact named above, Ty Mitchell (Assistant Director),  Karen Cassidy and Emmy Rhine Paule (Analysts-in-Charge), Mark  Abraham, Joy Booth, Ann Czapiewski, Brenda S. Farrell, Robert Gebhart,  Gretta Goodwin, Amalia Konstas, Lisa Pearson, Cynthia Saunders,  Andrea Starosciak, Jon Ticehurst, and Peter Verchinski made significant  contributions to this report.

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Census data is used for things like congressional redistricting and to allocate billions each year in federal funds. Consequently, it is necessary that the Census Bureau ensures that the data it collects is accurate and of high quality.

We described the Census Bureau’s plans to resolve data quality issues facing the 2020 Census, like missing or incomplete responses.

For instance, to resolve missing household responses, the Bureau plans to draw data from, among other sources, prior census records and similar nearby households to determine whether a housing unit exists, whether it is occupied, and by how many people.