The Office of Management and Budget (OMB) defines a “Metropolitan Statistical Area” as a population nucleus of 50,000 or more, generally consisting of a city and its immediate suburbs, along with adjacent communities having a high degree of economic and social integration with the nucleus.
MSA’s are designated by counties, the smallest geographic units for which a wide range of statistical data can be attained. However, in New England, MSA’s are designated by cities and towns since these subcounty units are of great local significance and considerable data is available for them.
Currently, an area is defined as an MSA if it meets one of two standards: (1) A city has a population of at least 50,000; (2) the Census Bureau defines an urbanized area of at least 50,000 people with a total metropolitan population of at least 100,000 (or 75,000 in New England). The Census Bureau’s definition of urbanized areas, data on commuting to work, and the strength of the economic and social ties between the surrounding counties and the central city determine which counties not containing a main city are included in an MSA. For New England, MSA’s are determined by a core area and related cities and towns, not counties. A metropolitan statistical area may contain more than one city of 50,000 and may cross State lines.