Metropolitan and micropolitan statistical areas (metro and micro areas) are geographic entities defined by the U.S. Office of Management and Budget (OMB) for use by Federal statistical agencies in collecting, tabulating, and publishing Federal statistics. The term "Core Based Statistical Area" (CBSA) is a collective term for both metro and micro areas. A metro area contains a core urban area of 50,000 or more population, and a micro area contains an urban core of at least 10,000 (but less than 50,000) population. Each metro or micro area consists of one or more counties and includes the counties containing the core urban area, as well as any adjacent counties that have a high degree of social and economic integration (as measured by commuting to work) with the urban core.
For the most recent lists of metropolitan and micropolitan statistical areas and their component counties, see the current definitions page. For additional information and data, visit the links below.
While OMB recognizes that a number of agencies, both inside and outside the Federal government, make use of the definitions of metropolitan and micropolitan statistical areas for nonstatistical programmatic applications, OMB defines the areas for statistical purposes only. In defining metropolitan and micropolitan statistical areas, OMB does not attempt to anticipate or take into account any nonstatistical uses that may be made of the definitions, nor will OMB modify the definitions to meet the requirements of any nonstatistical program. Questions about how metropolitan or micropolitan statistical areas are used within any particular nonstatistical program should be directed to the agency that administers that particular program.
For more information, contact the Population Distribution Branch at (301) 763-2419.