United States Census
Contents
Geography
The Census follows this hierarchy:
- states
- counties
- tracts
- block groups
- blocks
Tracts are demographically and economically homogeneous with a population of around 4,000. Tract boundaries are usually visible features (i.e. rivers). Tracts are reviewed every decade for subdivision but generally are static.
Block groups usually have between 250 and 550 housing units.
A census block is the smallest geographic unit used. Blocks are often the same as ordinary city blocks, bounded by roads. Blocks change every decade.
Frequency
The Census is conducted every 10 years, i.e. 2020.