Differences between the Decennial Census and the ACS
Beginning in 1940, the census began to incoporate sampling procedures to collect supplementary data (released as supplementary reports of various kinds).
In 1960, the census was conducted using a short form, asked of every household, and a much longer, two-part form, asked of 20% of households.
By 1970, a short form went out to every household, and the long form, sample data, was asked of 1-in-6 households.
1980 - 2000:
- SF 1 -- Data is from the short list of questions asked of every household
SF 3 -- Data is from a much longer, more detailed, list of questions asked of 1-in-6 households.
2010 - the present:
- Decennial Census: A brief questionnaire is sent to every household. More detailed data is available from the American Community Survey (ACS).
American Community Survey: The ACS is a continuous, rolling, survey of 1-in-8 households. Data is released in 1-year, 3-year*, and 5-year estimates.
*ACS 3-year estimates have been discontinued.
See: Comparing ACS data