Metropolitan and Micropolitan Statistical Areas
Metropolitan and micropolitan statistical areas (metro and micro areas) are geographic entities delineated by the 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.
Delineations and Standards
Current Delineations (Released February 2013)
2010 OMB Standards [PDF] for Delineating Metropolitan and Micropolitan Statistical Areas
(Note: The new delineations based on the 2010 standards were announced by OMB in 2013.)
Source: United States Census Bureau