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U.S. Census of Population and Housing Basics : Surveys & Data Sets

Introduction to finding demographic and housing facts and statistics collected by the U.S. Census Bureau.


In Census language, a survey is "a data collection activity involving observation or questionnaires for a sample of a population. (A census is a 100-percent sample survey; it collects information about every member of a population." (Entry from the Census Glossary.)

Examples of surveys:

  • American Community Survey
  • Annual Survey of Manufacturers
  • Decennial Census of Population and Housing
  • Economic Census

Decennial Census--100 percent survey

The Decennial Census of Population and Housing is a 100% survey; it collects information about every member of a population.

As of January 2021, data from the 2020 Decennial Census is being tabulated and verified It is not yet available to the public.  See the Important Dates page from the Census Bureau for updates on data availability from the 2020 Decennial Census.

Previous Decennial Censuses

In 2010, the Census Bureau collected the following information about every person in the country:

  • Household relationship
  • Sex
  • Age
  • Hispanic origin
  • Race
  • Tenure (Own or rent)

In recent Decennial Censuses before 2010, the questionnaire people filled out to collect this information was called the short form. Sample data was collected via the long form. With the 2010 Census, the American Community Survey replaced the long form.

Data from the 100% survey is made available via

  • Summary File 1, with cross-tabulations of
    • Age
    • Sex
    • Households
    • Families
    • Relationship to householder
    • Housing units
    • Detailed race
    • Detailed Hispanic or Latino origin groups
    • Group quarters
  • Summary File 2 makes the data from Summary File 1 available for specific race and ethnic groups within a community.

Detailed data--sample data/American Community Survey

Starting with the 1940 Census, and ending with the 2000 Census, the Census Bureau used sampling techniques to develop more data on the U.S. population.

Sampling meant asking additional questions of a subset, or sample, of the population during the Decennial Census, then used weighting formulas so the data would be representative of the larger population.

The additional questions asked of the sample of the population changed over time (see Index of Questions asked over the years), but included more questions on demographics (like what country a person was born in) and housing (like number of rooms in a house), as well as questions about educational attainment, income, employment, and veteran status.

For the 1990 and 2000 Decennial Censuses, sample data was published in Summary File 3 and 4 products.

In 2005, the Census Bureau started collecting detailed data from a sample of the population via the American Community Survey (ACS) (a bit of its history), which is an ongoing survey which provides data more frequently than the Decennial Census. It is sent to a small percentage of the population on a rotating basis throughout the decade. No household will receive the survey more often than once every five years.

The American Community Survey asks questions about

  • age
  • sex
  • race
  • family and relationships
  • income and benefits
  • health insurance
  • education
  • veteran status
  • disabilities
  • where you work and how you get there
  • where you live and how much you pay for some essentials


Here's a more detailed list of subjects covered  by the ACS (page from the Census Bureau).


Frequency of ACS
American Community Survey 1- and 5-year estimates are period estimates, which means they represent the characteristics of the population and housing over a specific data collection period. Data are combined to produce 12 months (1 year),  or 60 months (5 years) of data.

Data set Data collected over Produced for areas with populations of
1-year 12 months 65,000+
5-year 60 months almost any size

There will be times when more than one ACS data set is available for an area. For guidance on when to use which data set, see the Census Bureau's page When to use 1-year, 3-year, or 5-year estimates. It means striking a balance between currency and sample size/reliability/precision.

The ACS did provide 3-year estimates between 2005 and 2013, but those have been discontinued.  Data was collected over 36 months, and produced for areas with populations of 20,000+ .


Comparing ACS Data: Guide from the Census Bureau on comparing ACS data from different ACS data sets, as well as 2010 and 2000 Decennial Census sets

Why This Matters

Different surveys ask different sets of questions.

Surveys are taken at different times.

Different surveys ask questions of different sets of people.

Subject Guide

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Beth Harper
Memorial Library
University of Wisconsin-Madison

Government Information Specialist