Geographic Terms and Concepts -
Core Based Statistical Areas and Related Statistical Areas

Core Based Statistical Areas (CBSAs) consist of the county or counties or equivalent entities 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 associated with the core.  The general concept of a CBSA is that of a core area containing a substantial population nucleus, together with adjacent communities having a high degree of economic and social integration with that core.  The term "core based statistical area" became effective in 2003 and refers collectively to metropolitan statistical areas and micropolitan statistical areas.  The U.S. Office of Management and Budget (OMB) defines CBSAs to provide a nationally consistent set of geographic entities for the United States and Puerto Rico for use in tabulating and presenting statistical data.  Current CBSAs are based on application of the 2000 standards (published in the Federal Register of December 27, 2000) with Census 2000 data.  The first set of areas defined based on the 2000 standards were announced on June 6, 2003; subsequent updates have been made to the universe of CBSAs and related statistical areas.  No CBSAs are defined in the Island Areas.  Statistical areas related to CBSAs include metropolitan divisions, combined statistical areas (CSAs), New England city and town areas (NECTAs), NECTA divisions, and combined NECTAs.

Combined New England City and Town Areas (Combined NECTAs) consist of two or more adjacent New England city and town areas (NECTAs) that have substantial employment interchange.  The NECTAs that combine to create a combined NECTA retain separate identities within the larger combined NECTA. Because combined NECTAs represent groupings of NECTAs, they should not be ranked or compared with individual NECTAs.

Combined Statistical Areas (CSAs) consist of two or more adjacent CBSAs that have substantial employment interchange.  The CBSAs that combine to create a CSA retain separate identities within the larger CSA.  Because CSAs represent groupings of metropolitan and/or micropolitan statistical areas, they should not be ranked or compared with individual metropolitan and micropolitan statistical areas.

Metropolitan Divisions are smaller groupings of counties or equivalent entities defined within a metropolitan statistical area containing a single core with a population of at least 2.5 million.  Not all metropolitan statistical areas with urbanized areas of this size will contain metropolitan divisions.  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/secondary county or counties through commuting ties.  Because metropolitan divisions represent subdivisions of larger metropolitan statistical areas, it is not appropriate to rank or compare metropolitan divisions with metropolitan and micropolitan statistical areas.  It would be appropriate to rank and compare metropolitan divisions.

Metropolitan Statistical Areas are CBSAs 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 or equivalent entities containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting.

Micropolitan Statistical Areas are CBSAs 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 or equivalent entities containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting.

New England City and Town Areas (NECTAs) are an alternative set of geographic entities, similar in concept to the county-based CBSAs defined nationwide, that OMB defines in New England based on county subdivisions—usually cities and towns.  NECTAs are defined using the same criteria as county-based CBSAs, and, similar to CBSAs, NECTAs are categorized as metropolitan or micropolitan.

New England City and Town Area (NECTA) Divisions are smaller groupings of cities and towns defined within a NECTA containing a single 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 through commuting ties.  Each NECTA division must contain a total population of 100,000 or more.  Because NECTA divisions represent subdivisions of larger NECTAs, it is not appropriate to rank or compare NECTA divisions with NECTAs.  It would be appropriate to rank and compare NECTA divisions.

Principal Cities of a CBSA (or NECTA) include the largest incorporated place with a population of at least 10,000 in the CBSA, or if no incorporated place of at least 10,000 population is present in the CBSA, the largest incorporated place or census designated place (CDP) in the CBSA.  Principal cities also include any additional incorporated place or CDP with a population of at least 250,000 or in which 100,000 or more persons work; any additional incorporated place or CDP with a population of at least 50,000 and in which the number of jobs meets or exceeds the number of employed residents; and any additional incorporated place or CDP with a population of at least 10,000 but less than 50,000 and at least one-third the population size of the largest place and in which the number of jobs meets or exceeds the number of employed residents.  Note that there are some places designated as principal cities of NECTAs that are not principal cities of a CBSA.

Core Based Statistical Area Codes—Metropolitan statistical areas, micropolitan statistical areas, NECTAs, metropolitan divisions, and NECTA divisions are identified using a five-digit numeric code that is assigned alphabetically based on title and is unique within the nation.  The combined statistical area and combined NECTAs are identified using a three-digit numeric code, also assigned alphabetically based on title and unique within the nation.  Codes, length, and ranges are:

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