- Decennial Census
Counts from the decennial census reflect the makeup of the population in the year of the decennial census. Between census years, the counts are restated and new files added to reflect changes in congressional boundaries.
Up until the 2010 Census there were data files from both the 100% count (persons, race/Hispanic origin, sex, age, household type) and from the long form sample count (wide range of socio-economic variables) are available. Starting in 2010 the Census was only a 100% count as the questions on socio-economic detail were moved to the ACS.
- American Community Survey (ACS)
This is a continuous survey with questions similar to what were asked in the decennial census long form. From it annual reports are produced. Counts from this source relate to the time span as referenced in the ACS file name. Data tables are available starting with the 109th Congress.