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Decennial Census of Population and Housing Technical Documentation

These documents refer to the decennial census conducted in the 50 U.S. states, Washington D.C., and Puerto Rico.

Technical documents are designed to help people use published statistics. The resources available for download may vary by census year and can include the following. 

Codebooks - Information about the files, including descriptive information on all of the variables.

Data Dictionary - A repository of information describing database attributes including identification of record codes and area characteristics, endnotes, and table section.

Historical Changes - Information for the current census year and prior census years.

Methodology - The methods we use to collect census data and produce the census results, including sampling, questions, collection, review, quality, weighting, etc.

Questionnaires - Find the most recent questionnaire and whether an archive of past questionnaires is available online.

Subject Definitions - Definitions of population, housing and other variables to help you understand the results of a census.

User Notes - Issues affecting the census, including design, collection, processing, tabulation, and release, to be better informed when analyzing stats.

  • 2020
  • 2010
  • 2000
  • 1990

Complete technical documentation for 2020 Census data products will be posted below once the corresponding data product is published. Planned release dates are listed for documentation that is not yet available.

User notes and subject definitions are found within each file, among other resources.

Additional Data User Guidance

Note: Additional data user guidance is forthcoming and will be published here once available. Please check back for updates.

pdf Disclosure Avoidance for the 2020 Census: An Introduction [1.6 MB]
This handbook describes the Disclosure Avoidance System in the context of the 2020 Census Redistricting Data (P.L. 94-171) Summary File.
pdf Disclosure Avoidance and the 2020 Census Redistricting Data: What Data Users Need to Know
This brief provides key information about disclosure avoidance for the 2020 Census Redistricting Data.
pdf Why the Census Bureau Chose Differential Privacy
This brief describing how disclosure avoidance methods are being applied to 2020 Census data products and implications of those methods for data users.
pdf Disclosure Avoidance and the 2020 Census: How the TopDown Algorithm Works
This brief describes how differential privacy works and is applied to the 2020 Census Redistricting Data and Demographic and Housing Characteristics File.
web Disclosure Avoidance Webinar Series
This webinar series explains the Census Bureau’s plans to apply modernized noise infusion algorithms to protect 2020 Census statistics from disclosure.

Redistricting Data (Public Law 94-171) Summary File

Demographic and Housing Characteristics File (DHC) and Demographic Profile (DP)

118th Congressional District Summary File

Planned release date: August 2023

Detailed Demographic and Housing Characteristics File A (Detailed DHC-A)

Planned release date: September 2023

Detailed Demographic and Housing Characteristics File B (Detailed DHC-B)

Planned release date: To be determined

Supplemental Demographic and Housing Characteristics File (S-DHC)

Planned release date: To be determined

Privacy-Protected Microdata Files (PPMF)

Planned release date: To be determined

Page Last Revised - May 25, 2023
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