Description: Census tracts are small and relatively permanent statistical subdivisions of a county or equivalent entity.
Local participants review and update census tracts prior to each decennial census as part of the Census
Bureau’s PSAP. The Census Bureau updates census tracts in situations where no local participant
existed or where local or tribal governments declined to participate. The primary purpose of census tracts
is to provide a stable set of geographic units for the presentation of decennial census data.
4-24
Census tracts generally have a population size of 1,200 to 8,000 people with an optimum size of 4,000
people. The spatial size of census tracts varies widely depending on the density of settlement. Ideally,
census tract boundaries remain stable over time to facilitate statistical comparisons from census to
census. However, physical changes in street patterns caused by highway construction, new development,
and so forth, may require boundary revisions. In addition, significant changes in population may result in
splitting or combining census tracts.
Census tract boundaries generally follow visible and identifiable features. Census tract boundaries may
follow legal boundaries (e.g., MCD or incorporated place boundaries in some states to allow for census
tract-to-governmental unit relationships where the governmental boundaries tend to remain unchanged
between censuses). State and county boundaries always are census tract boundaries in the standard
census geographic hierarchy.
In a few rare instances, a census tract may consist of noncontiguous areas. These noncontiguous areas
may occur where the census tracts are coextensive with all or parts of legal entities that are themselves
noncontiguous