One of my colleagues was doing a presentation about various free data sources. This is what was written about the Census:
The Census Bureau conducts a number of programs. The most famous is the decennial Census, mandated in Article 1 Section 2 of the U.S. Constitution. The 2010 Census had only handful of question pertaining to race, Hispanic origin, gender, age, and whether the address is one’s primary residence.
Census 2000 was the last iteration to contain a long form for approximately 1 household in 6 to fill out. That information included data about income, education, mobility, nativity,, ancestry, disability, military service, housing stock and more. These types of data are now being captured in something called the American Community Survey, which, starting in 2010, will be released every year for all geographies. Because the sample size is smaller than the Census 2000 long form sample, there are data releases for periods of 1-, 3- or 5-year groupings, depending on the size of geographies. There are reasoning behind these breakdowns, but suffice to say here that one ought not ever compare 1-year data with 3-year or 5-year data.
There is also an Economic Census, measuring the country’s businesses every five years, reflecting those years ending with 2 and 7. Since the survey isn’t sent out until the very end of the target years, data for these years released don’t start coming out until a couple years after the named years. Incidentally, there are separate surveys for agriculture and governments conducted at the same time.
If you go to Census.gov, you’ll see headings such as People & Households and Business & Industry in the center of the page. Although not immediately obvious, these terms are hyperlinks that may provide you with easier access to Census data.