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A general term, originating from the USA, to describe a very large urban settlement. Metropolitan districts were first defined in the 1910 US census by grouping large central cities (administrative districts) with their contiguous suburbs into single data-reporting units. The term was changed to \'Standard Metropolitan Area\' in 1950 and to \'Standard Metropolitan Statistical Area\' (SMSA) in 1960, when 219 were defined: the criteria for defining SMSAs were population size, population density, and occupational structures, and the basic building blocks were counties. Within SMSAs the US Bureau of the Census also defines \'Urbanized Areas\', comprising the built-up portions only. The system was restructured in 1990, creating three types of area:
{img src=show_image.php?name=2022.gif } Metropolitan Statistical Areas (MSAs) are groups of counties (except in New England) comprising a central city with a population of 50,000 or more surrounded by an urbanized area (defined, as before, by population density and occupational structures) whose total population exceeds 100,000; {img src=show_image.php?name=2022.gif } Consolidated Metropolitan Statistical Areas (CMSAs) are larger than MSAs, with their urbanized areas having populations of at least 1,000,000; and {img src=show_image.php?name=2022.gif } Primary Metropolitan Statistical Areas (PMSAs) are separate components of CMSAs with distinct characteristics: the Detroit/Ann Arbor CMSA has two PMSAs, for example, focused on the two central cities, whereas the New York/New Jersey/Long Island CMSA is divided into 10 separate CMSAs.Many countries now have defined metropolitan areas, on widely varying criteria. (RJJ) |
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