Decennial Census (latest is 2010)
The most comprehensive Census survey is the Decennial Census, which counts everyone in the U.S. It happens every ten years (in years ending in 0). Basic data on the population (age, sex, race) is available by the beginning of the next year (i.e., 2011, 2021, etc.). More detailed information is released later, sometimes up to 3 years after the Census is taken.
This survey is taken continually, as a way to update information in between Decennial Censuses. However, this is a true survey, and not a complete count. It is taken by asking questions of samples of the population. (For more information on the ACS, see this box.)
In Census tables you will see 1-year, 3-year and 5-year ACS estimates. Here is a summary of what these distinctions mean:
Can you compare data from different surveys?
Yes, in some cases. Below is a link to a summary of what should and should not be compared. The page includes links to a tool that will give you precise tables to compare.
The Census Bureau also conducts surveys of economic and governmental activity. These Censuses are conducted every five years. Here are portals to this data:
(For more information and links, see the appropriate tabs in this Research Guide.)