About these guides
Census data is so voluminous and complex to describe that we think it's best to divide up our Census LibGuides into In the Library and On the Web sections.
Use the On the Web tab if you need:
- Recent Census information. Most, if not all, Census data after 2000 is available online only.
- To download tables for manipulation in spreadsheet or other types of software
- To know how Census material is organized and accessed online
Use the In the Library tab if you need:
- Older Census information that is not digitized
- To know what's available in the Library to be checked out
- To know how the Library's printed Census material is organized
Understanding Census Data
Understanding the limitations of Census data is very important to avoid wasting time looking for non-existent information. Some general caveats are explained in the box below.
More complicated questions, such as issues involved in the comparability of data across Census surveys and the compilation of racial and ethnic statistics, are addressed in the tabs above. There is also a tab that goes into some detail regarding the importance of geography in using Census data.
What you need to know before searching for any Census data
Census data is not available instantly
As required by the Constitution, the Census Bureau conducts a complete count of residents of the U.S. every ten years. Simple counts of people in states and areas must be available by the beginning of the year following the Census because this data is used to apportion Congressional seats. The other data (income, education, etc.) generated by the Census surveys usually takes a few years to become available. This detailed data, giving social and economic characteristics of the population of small geographical areas, is usually not available until at least three years after the Census was taken.
The more detailed the statistics one searches for, the less detailed are the geographical areas for which the statistics are available. For example, in past Censuses, general population counts were published for places as small as 1,000 people. But poverty status figures were given only for places as small as 2,500. Detailed cross-tabulations of poverty status and educational level may only be given for large (more than 250,000) cities. Thus, two parameters are important when selecting a Census report to study: the kind of statistics one needs, and the geographical area of interest. For more information on Census geography, see the Special Issues tab in this Guide.
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 basic information (e.g.: age, sex, race) is obtained from all residents, whereas other, more detailed questions (e.g.: income, education, employment status) are only asked of a sample. And some questions are not asked at all, (for example, "what is your religion?") which means that no data on these subjects is available from the Census Bureau. For more information on the importance of Census methodology, see the Comparability tab in this Guide.