2020 Census

Esri Methodology Statement, December 2021

Overview 

The United States Census is a once-a-decade exercise to capture a snapshot of the nation’s population “once, only once, and in the right place.” The national head count is always a complex endeavor; however, the 2020 Census was like no other decennial census. The 2020 Census operations were forced to cope with the COVID-19 pandemic, record-setting wildfire and hurricane seasons, civil unrest in many urban centers, as well as political challenges around a potential citizenship question and how to count undocumented immigrants for congressional apportionment. Given these unprecedented challenges, the United States Census Bureau should be commended for completing the census in a timely manner and accounting for 99.98 percent of all housing units. The 2020 Census was also the first census in the United States to offer online response. This response mode was an enormous success with around four of every five households responding online. 


Data products

Data from the 2020 Census is planned to be primarily released through four data products. These data releases are currently ongoing as the Census Bureau is operating under a revised data product release schedule due to the impacts of the COVID-19 pandemic. Current 2020 Census data products are as follows: 

  • Apportionment Data, released April 26, 2021. This product, consisting of the counts of the resident population at the state level, is used to apportion the 435 seats in the U.S. House of Representatives among the 50 states.
  • Redistricting Data (P.L. 94-171), released August 12, 2021. This product consists of census data at the block level and above for six tables: Race; Hispanic or Latino, and Not Hispanic or Latino by Race; Race for the Population 18 Years and Over; Hispanic or Latino, and Not Hispanic or Latino by Race for the Population 18 Years and Over; Group Quarters Population by Group Quarters Type; and Occupancy Status. This product is used by the states to delineate voting districts to be used for the next 10 years.
  • Demographic and Housing Characteristics file (DHC), release date not announced (as of December 2021). This product will replace the Summary File 1 (SF1) data from the 2010 Census. This data will provide basic information on population and housing.
  • Detailed Demographic and Housing Characteristics file (DDHC), release date not announced (as of December 2021). This product will replace the Summary File 1 (SF1) and Summary File 2 (SF2) data from the 2010 Census. This data will provide detailed information on population and housing. In addition, this product will contain data items with reconciled discrepancies between the population and housing universes resulting from the 2020 Census privacy protections.

Esri value added to 2020 redistricting data

The 2020 Census Redistricting Data was released by  Esri Demographics  for the United States and the territory of Puerto Rico. This product allows data users to access all redistricting data down to the block group level through Esri’s ArcGIS GeoEnrichment Service, ArcGIS Business Analyst web/mobile apps, ArcGIS Business Analyst Pro, and ArcGIS Community Analyst. Users who are interested in census block-level redistricting data can access those files in  Living Atlas of the World  and through  Esri’s Redistricting application . These ArcGIS Living Atlas layers can be  imported into Business Analyst  to satisfy additional workflows.

Esri has added value to the 2020 redistricting data in several ways:

1. Facilitation of temporal analysis

Esri converted select SF1 totals from the 2000 Census and 2010 Census to 2020 geography, enabling temporal analysis for total population, household population, group quarters population, households, housing units, and average household size. Converting 2000 and 2010 data to 2020 geographic boundaries enables comparisons across three time periods. Converting this data required the creation of a correspondence file from 2000 and 2010 block groups to 2020 block groups built from 2000 and 2010 block to 2020 block group relationships. To establish these relationships between vintages, Esri incorporates the block-to-block relationship files from the Census Bureau.[1] Esri created versions of these files that were required for the 2000 to 2020 block relationships since this file is unavailable from the Census Bureau. These relationship files are used to build out all 11 geographic schemas for select SF1 2000 and 2010 data in 2020 geography. 

2. User-defined areas

ArcGIS Business Analyst as well as GeoEnrichment within ArcGIS Pro and ArcGIS Online allow users to build reports and infographics for any user-defined area. These systems use 2020 Census block weights in the data apportionment process. 

3. Non-Census geographies

For the United States, the 2020 redistricting data is available in 11 geographic schemas, including HERE residential ZIP Codes and Nielsen Designated Market Areas (DMAs). Neither schema was part of the Census Bureau’s data release. For Puerto Rico, data is available for eight geographic schemas, including HERE residential ZIP Codes.

4. Calculated items

Esri produces a set of derived statistics, including compound annual growth rates for all totals, vacant housing units, average household size, population density, and Esri’s Diversity Index.

5. Hispanic by Race and Hispanic by Race for the population under the age of 18

The Census Bureau releases tables for the non-Hispanic population by race and non-Hispanic population by race for the population 18 years of age and older. Esri uses the released census data to calculate the residual Hispanic data tables. These include Hispanic population by race and Hispanic population by race for the population under the age of 18. 


Census changes to 2020 redistricting data 

Every decennial census effort intends to improve on the prior decennial census. In addition to allowing for online response, there are a few other significant changes to how the 2020 Census data was collected and tabulated. The 2020 Census redistricting data included notable changes for group quarters as well as race and ethnicity data. 

  • The 2020 Census was the first time that group quarters population by major group quarters type was released in the redistricting data. In prior censuses, group quarters data was part of a later data release. Group quarters data was included in the 2020 Census redistricting data product to allow several states to count prisoners at their home addresses instead of at the location of the prisons.[2] In addition, counting the group quarters population was a significant challenge for the 2020 Census due to the COVID-19 pandemic. During the time that group quarters data is typically collected, many nursing homes were locked down and not allowing visitors, and college campuses were largely empty. Given these challenges, the Census Bureau was forced to revise its standard procedures for counting the population in these facilities.
  • The Census Bureau implemented subtle but important changes to improve the race and ethnicity questions on the 2020 decennial census questionnaire. These consisted of changes to the wording and examples provided on the form for questions related to race and ethnicity. “Negro” was removed, and “Guamanian or Chamorro” was changed to “Chamorro.” Most importantly, the write-in instructions for “Some Other Race” were changed from “Print race” to “Print race or origin.” The maximum number of characters processed by the census for write-in responses was lengthened from 30 to 200 characters. Write-in responses were processed into a maximum of six categories, which is up from two in the 2010 Census.[3]

Differential privacy

The most significant departure from the 2010 Census is the Disclosure Avoidance System (DAS) used for the 2020 Census. The Census Bureau is required to keep the collected information confidential for 72 years, and under Title 13, any individual must be protected from being identifiable in published data. In past censuses, the Census Bureau used various forms of disclosure avoidance to ensure privacy protection. These techniques historically consisted of table suppression and data swapping. 

The 2020 Census opens a new era of disclosure avoidance with the implementation of differential privacy. Differential privacy is a formal statistical technique used to “inject noise” into the tabulations to better safeguard individual privacy. The DAS consists of two components: differential privacy and post-processing adjustments. Differential privacy adds statistical noise to the data to protect individual privacy while post-processing is used to adjust the noisy data so that it looks like census data that users are accustomed to receiving. These adjustments ensure that fractions or negative values are removed, components sum to their respective table totals, and impossible or improbable statistics are kept to a minimum. State-level population and housing unit statistics at every geographic level are actual counts and do not have noise added. All other statistics are subjected to noise and should not be treated as actual counts.  

There are positive and negative aspects to using differential privacy as part of the 2020 Census DAS. In the past, the magnitude of data swapping in the decennial census was not disclosed. For the 2020 Census, the Census Bureau has openly shared its statistical methods while working with stakeholders to fine-tune the DAS to protect privacy but also produce data that is “fit for use.” However, census data users are likely to find it difficult to understand the magnitude of noise in differentially privatized data. While the post-processing does “fix” many of the issues caused by the application of the differential privacy method, the DAS still produces many impossible and improbable results at smaller levels of geography—something that did not exist in prior decennial census releases.

The implementation of differential privacy is also likely to impact additional census data products. The 2020 Census DAS has inherent limitations that are likely to reduce both the number of data tables and the geographic granularity of the data in the DHC and DDHC. In summary, census data users will likely have less data overall, and in particular, less small area data to work with compared to prior censuses.


Endnotes


Additional resources

For users that would like to better understand how differential privacy impacts 2020 Census data, Esri has compiled a  Differential Privacy Resources page  dedicated to educating our users about changes in the Census 2020 data releases and is committed to helping our users leverage census data using best practices. As more information and data are released this document and additional Census 2020 documentation will be updated.  

For more information about Esri's Updated Demographics data, visit  esri.com/esri_data  or call 1-800-447-9778.


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