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Census Data

Learn more about how Census data is collected and processed.

Overview

The United States Census, a count of every person, takes place every 10 years, most recently in 2020. Due to factors such as the COVID-19 pandemic, there have been concerns about whether those who are historically undercounted would be fully counted, as well as about the quality of data collected and whether target deadlines would be met.

Why this is important

It is legally required that redistricting maps meet equal population criteria, which requires census data. Besides being used in redistricting, data collected by the Census is used to allocate billions in federal funding, determine the apportionment of Congressional seats, and help with community planning.

See what the Census says about the importance of data

Who is included?

The Census sends surveys to all U.S. residential structures to count everyone living in the country. “Residential structures” include group housing such as correctional facilities, college dormitories, military barracks, and retirement homes.

When is data collected?

The Census Bureau started its planning process in 2013 and officially began the count on January 21, 2020 in Alaska. For most people, the count started on March 13, 2020 and was to conclude on July 28, 2020, but was extended to October 15, 2020 because of the health pandemic. Its official deadline to deliver apportionment counts to the President was no later than December 31, 2020; however, that deadline was missed. By April 1, 2021, the Census Bureau is required to send redistricting counts to the states, which will use those data to redraw congressional and state legislative districts based on population changes. The Census Bureau has indicated it cannot meet the April 2021 deadline for sending redistricting data, but has not yet identified a new date.

What information is collected?

Census surveys ask about the number of people living in the same residence, how they are related, and collect information on each member of the household. Questions include age, sex, race, and Hispanic origin on each person. There is no citizenship question on the 2020 Census.

How is this data collected?

How is this data collected? The Census Bureau sent out invitations to most households to complete their responses online, by phone, and by mail. Field workers then followed up with those who did not respond.

What is an undercount?

In every demographic group, some people are missed in the Census, and some people are counted more than once (or included inappropriately) in the Census. When the number of people missed is larger than the number of people counted more than once, it produces a net undercount. When the number of people counted more than once is larger than the number of people missed it produces a net overcount. Historically, people of color, young children (age 0–4), renters, and low-income individuals are among those consistently undercounted. Often, these demographic categories are called “hard-to-count” or “hard-to-reach.”

How is this data processed?

Between collection and delivery of data, the Census Bureau processes data through quality control checks, removal of personally identifiable information, and approaches for filling in missing information. Many of these processes are aimed at ensuring accuracy and privacy. Miscounts can mean the loss or gain of a Congressional seat for the next decade, improper allocation of federal funds, or poor or inaccurate community planning.

How is confidentiality protected?

An important legal requirement is that information about individuals collected through the Census is kept private. The Census Bureau has determined that past methods such as swapping and cell suppression to balance privacy and accuracy is no longer sufficient. Instead, the Bureau’s newest disclosure avoidance approach is called differential privacy. The differential privacy policy and approaches are still being refined as of the start of 2021.

How is this used in redistricting?

The data provided to the states through redistricting files is given at the block level, thereby providing the level of detail needed to draw district boundaries. Such granularity makes the differential privacy approaches (discussed above) even more important. If the balance is weighed too heavily on privacy, it may mean a loss of accuracy and district lines may not properly reflect who is living in certain locations. If the balance is weighed too heavily on accuracy, it may mean a loss of privacy which also is unacceptable.

Where can this data be found?

The 2020 Census data will become available some time in 2021. The latest data are available at Data.census.gov