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Micropolitan Statistical Areas were first introduced by the Office of Management and Budget (OMB) in June 2003 as part of the OMB redefinition of Federal Statistical Areas that occurs after each decennial census. The new micropolitan areas differ from their Metropolitan Statistical Area counterparts only in urban core size. A metropolitan area is defined around an urbanized area of 50,000 or more population, whereas a micropolitan area contains one or more urban clusters with a population of at least 10,000 but less than 50,000. Each area of either type then takes in adjacent territories that have a high degree of social and economic integration with the urban core, as measured by commuting ties. Because both of these types of area are based on urban cores, they are collectively referred to as Core-Based Statistical Areas (CBSAs).
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