The 2020 Census is comprised of the Redistricting (P.L. 94-171 Redistricting Data) and the Demographic and Housing Characteristics File (DHC) which is very similar to their Summary File 1 (SF1) data release in 2010. These are both 100% counts of the US population and because of this have a more limited scope of questions. They are considered the official decentennial (occurring every ten years) census. A supplementary data set is the American Community Survey 2016-2020 (ACS 2020) which contains a richer demographic view of Americans. The ACS is not officially part of the census but has replaced the "Long Form" or SF3 that was historically part of the census. This is data that the USCB models from a longer questionnaire that is only sent to a subset of people (about 1 in 60 households annually) ) and then the USCB models it so that it represents the country as a whole.
What Data is Available in Each Data Set
- 2020 Redistricting - Public Law (P.L.) 94-171 requires the Census Bureau to provide only counts of the total population for a variety of geographic areas to be used for the redistricting process. In addition, other data items such as race, ethnicity, voting age and housing unit tallies are included in this data set.
- 2020 Demographic and Housing Characteristics (DHC2020) – the old Summary File (SF1) – is also a complete (100 %) data count. It has a more robust data set. It includes all age breakouts (including single year ages at the tract level and above), race by Hispanic origin and housing variables like households, tenure (own/rent) and even group quarters.
- 2020 Block Data files – the Demographic and Housing Characteristics (DHC) is released down to the Block level. You can get most of the DHC variables at the block level. There are some exceptions that for confidentiality you can’t get (like single year ages by race – those aren’t available until you get to the tract level).
- American Community Survey (ACS) - while not officially part of the 2020 Census this data set replaces the "Long Form" or SF3 released in prior census years. It includes variables such as income, housing value, employment, ancestry, educational attainment, language spoken, etc. that are not available in either the Redistricting or DHC data sets. The other great advantage of the ACS is that it is released annually as opposed to the other two which are released every 10 years. This means that these most important variables are constantly being refreshed.