Metropolitan area
United States

As of February 28, 2013, the United States Office of Management and Budget (OMB) defined 1,098 statistical areas for the metropolitan areas of the United States and Puerto Rico. These 1,098 statistical areas comprise 929 Core-Based Statistical Areas (CBSAs) and 169 Combined Statistical Areas (CSAs). The 929 Core-Based Statistical Areas are divided into 388 Metropolitan Statistical Areas (MSAs – 381 for the U.S. and seven for Puerto Rico) and 541 Micropolitan Statistical Areas (μSAs – 536 for the U.S. and five for Puerto Rico). The 169 Combined Statistical Areas (166 for the U.S. and three for Puerto Rico) each comprise two or more adjacent Core Based Statistical Areas.

The Office of Management and Budget defines a Metropolitan Statistical Area as one or more adjacent counties or county equivalents that have at least one urban area of at least 50,000 population, plus adjacent territory that has a high degree of economic and social integration with the core as measured by commuting ties. The OMB then defines a Combined Statistical Area as consisting of various combinations of adjacent metropolitan and micropolitan statistical areas with economic ties measured by commuting patterns. The Office of Management and Budget further defines a core-based statistical area (CBSA) to be a geographical area that consists of one or more counties (or equivalents) anchored by an urban center of at least 10,000 people plus adjacent counties that are socioeconomically tied to the urban center by commuting.
keywords:letter_frequency, length_constraints:number_sentences[7], oulipo:avoid_letter[a]