Definitions of Key Census Statistical Terms

Reading census definitions to understand core demographic information related to zip codes is sometimes a difficult exercise.  We've found it helpful to understand the key definitions that the Census uses in referring to some of its statistical areas such as MSA, CBSA, and PMSA.  We've included the common definitions below.

Census designated place.--A statistical geographic entity that is equivalent to an incorporated place, defined for the decennial census, consisting of a locally recognized, unincorporated concentration of population that is identified by name.

Central county.--The county or counties of a Core Based Statistical Area containing a substantial portion of an urbanized area or urban cluster or both, and to and from which commuting is measured to determine qualification of outlying counties.

Combined Statistical Area.--A geographic entity consisting of two or more adjacent Core Based Statistical Areas (CBSAs) with employment interchange measures of at least 15. Pairs of CBSAs with employment interchange measures of at least 25 combine automatically. Pairs of CBSAs with employment interchange measures of at least 15, but less than 25, may combine if local opinion in both areas favors combination. Core.--A densely settled concentration of population, comprising either an urbanized area (of 50,000 or more population) or an urban cluster (of 10,000 to 49,999 population) defined by the Census Bureau, around which a Core Based Statistical Area is defined.

Core Based Statistical Area (CBSA).--A statistical geographic entity consisting of the county or counties associated with at least one core (urbanized area or urban cluster) of at least 10,000 population, plus adjacent counties having a high degree of social and economic integration with the core as measured through commuting ties with the counties containing the core. Metropolitan and Micropolitan Statistical Areas are the two categories of Core Based Statistical Areas.

Employment interchange measure.--A measure of ties between two adjacent entities. The employment interchange measure is the sum of the percentage of employed residents of the smaller entity who work in the larger entity and the percentage of employment in the smaller entity that is accounted for by workers who reside in the larger entity.

Geographic building block.--The geographic unit, such as a county, that constitutes the basic geographic component of a statistical area. Main city or town.--A city or town that acts as an employment center within a New England City and Town Area that has a core with a population of at least 2.5 million. A main city or town serves as the basis for defining a New England City and Town Area Division.

Main county.--A county that acts as an employment center within a Core Based Statistical Area that has a core with a population of at least 2.5 million. A main county serves as the basis for defining a Metropolitan Division. Metropolitan Division.--A county or group of counties within a Core Based Statistical Area that contains a core with a population of at least 2.5 million. A Metropolitan Division consists of one or more main/secondary counties that represent an employment center or centers, plus adjacent counties associated with the main county or counties through commuting ties.

Metropolitan Statistical Area.--A Core Based Statistical Area associated with at least one urbanized area that has a population of at least 50,000. The Metropolitan Statistical Area comprises the central county or counties containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county as measured through commuting.

Micropolitan Statistical Area.--A Core Based Statistical Area associated with at least one urban cluster that has a population of at least 10,000, but less than 50,000. The Micropolitan Statistical Area comprises the central county or counties containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county as measured through commuting.

New England City and Town Area (NECTA).--A statistical geographic entity that is defined using cities and towns as building blocks and that is conceptually similar to the Core Based Statistical Areas in New England (which are defined using counties as building blocks). New England City and Town Area (NECTA)

Division.--A city or town or group of cities and towns within a NECTA that contains a core with a population of at least 2.5 million. A NECTA Division consists of a main city or town that represents an employment center, plus adjacent cities and towns associated with the main city or town, or with other cities and towns that are in turn associated with the main city or town, through commuting ties.

Outlying county.--A county that qualifies for inclusion in a Core Based Statistical Area on the basis of commuting ties with the Core Based Statistical Area's central county or counties. Outside Core Based Statistical Areas.--Counties that do not qualify for inclusion in a Core Based Statistical Area.

Principal City.--The largest city of a Core Based Statistical Area, plus additional cities that meet specified statistical criteria.

Secondary county.--A county that acts as an employment center in combination with a main county or another secondary county within a Core Based Statistical Area that has a core with a population of at least 2.5 million. A secondary county serves as the basis for defining a Metropolitan Division, but only when combined with a main county or another secondary county.

Urban area.--The generic term used by the Census Bureau to refer collectively to urbanized areas and urban clusters.

Urban cluster.--A statistical geographic entity to be defined by the Census Bureau for Census 2000, consisting of a central place(s) and adjacent densely settled territory that together contain at least 2,500 people, generally with an overall population density of at least 1,000 people per square mile. For purposes of defining Core Based Statistical Areas, only those urban clusters of 10,000 more population are considered.

Urbanized area.--A statistical geographic entity defined by the Census Bureau, consisting of a central place(s) and adjacent densely settled territory that together contain at least 50,000 people, generally with an overall population density of at least 1,000 people per square mile.