Skip to main content

Census Basics

summary of important basic information on finding and using Census data

What you need to know before searching for any Census data

Geography matters

The more detailed the statistics one searches for, the less detailed are the geographical areas for which the statistics are available. For example, usually general population counts are reported for places as small as 1,000 people. But poverty status figures are given only for places as small as 2,500. See the Geography tab for more information.

Not all data is created equal, and some isn't created at all

Information contained in the Census volumes is collected from questionnaire responses. Some questions are asked of everyone, and some only of a sample. Be aware of this distinction when making comparisons. (See more information about comparing Census data in this Guide.)

The data available depends up on the questions asked. Much general (age, sex, race) and detailed (income, education, ancestry, veteran status, etc.) information about the population is collected. But much is not. Some examples of topics that are not covered in Census questionnaires are: religion, political party, opinions.

In addition, keep in mind that the Census counts people at specific points in time. It does not have any information regarding mortality or causes of death among the population, although it has aggregate counts of deaths as part of its population change tables.

Individuals vs. Households

Census questionnaires are sent to households, but of course they count individuals within the household. Some data is therefore given for households (for example: household income) and some for individuals. Be sure you are looking at the right numbers for the data you wish to find.

Census data is not available instantly

Decennial Census counts happen every ten years (in years ending in 0) and basic numbers (people by age, race, and sex) are available at the beginning of the next year. More detailed data on the population is not released for another year or two. American Community Survey counts help fill in the gaps. See the "Census Surveys" tab for more information on the ACS.

Introduction to Census data

signpostThe Census Bureau collects and reports vast amounts of data. Looking for the information you need can be overwhelming. But we hope the basic tips in this guide will make the process easier.

For more detailed information on these sources and topics, see these other Research Guides:

More information about the Census Bureau and Census surveys

The Census Bureau is the major agency for collecting and disseminating data on the American people, on businesses, and on housing units. Here are some big-picture political and ethical issues to keep in mind when responding to Census surveys and when using Census data:

  • All the questions asked in Census surveys must have a legislative purpose and authorization, and the Office of Management and Budget has the final say on what questions are asked. The data is often needed by other government agencies to be able to do their jobs effectively. General legal authority for the Census Bureau's activities is found in Titles 13 and 26 of the U.S. Code. For more details on the Bureau's mission and activities, see this "What We Do" page from their website.
  • Census data is always collected and disseminated in order to provide aggregate statistical information. Data is not displayed on any of their tables if a geographic unit is so small that individual people, households, or businesses might be identifiable.
  • The data on Census forms is not shared with other agencies. The enumeration forms, which give data on individuals and addresses (useful for genealogical research) are only released 70 years after being filled out. For example, the most recent forms now available are those for the 1940 Census. See the National Archives for more information.