Description:
Metropolitan areas are whole counties or combinations of counties centering on a substantial urban area. In New England, where counties are not functioning political entities, metropolitan areas are composed of cities and towns rather than whole counties.
Comparability:
Despite the terminological and technical issues that follow, the concept of "metropolitan area" has remained essentially the same throughout the years. However, there are three basic comparability issues that all users should be aware of:
1. Most metropolitan areas encompassed less territory during earlier years than they did in later ones, as the census reconsidered and adjusted the boundaries of each metropolitan area to account for growth during each ten-year period.
2. As population grows and people migrate to urban areas, new metropolitan areas regularly emerge, so the number of them has steadily increased since the concept was first invented.
3. There were slight variations in how the concept was defined from census to census. The special notes on each year (below) offer an overview of how the metropolitan concept has changed over time.
Metropolitan areas have been referred to by several different names over the years.
* In 1950 the term was Standard
Metropolitan Area (SMA).
* In 1970 and 1980, the term was Standard
Metropolitan Statistical Area (SMSA).
* In 1990 it was Metropolitan Area (MA), which included:
1. free-standing Metropolitan Statistical Areas (MSAs) and,
2. Consolidated Metropolitan Statistical Areas (CMSAs) consisting of two or more economically and socially linked metropolitan areas, called Primary Metropolitan Statistical Areas (PMSAs). Many PMSAs were separate SMSAs or SMAs before 1990.
Prior to 1950, the census did not define metropolitan areas, though it did employ a concept termed "metropolitan districts".
Despite the terminological shifts, the general concept is the same for all years: A metropolitan area (whether an SMA, SMSA, MSA, or a CMSA containing several PMSAs) is an area consisting of a large population center and adjacent communities (usually counties) that have a high degree of economic and social interaction with that center. Metropolitan areas often cross state lines. Some Metropolitan areas contain more than one central city. In previous years, those cities may either have been the central cities of separate metropolitan areas or not part of any metropolitan areas.
Metropolitan areas are listed according to their current definition and have a five digit code. Because of changes in the county composition of metropolitan areas over time, users may want to reconstruct metropolitan areas using the county level files.
1970 SMSAs were essentially the same as what were previously called SMAs, although in some cases there was no single central city of 50,000+ residents, but instead two or more contiguous cities of 15,000+ residents each with a combined population of 50,000+. If adjacent counties each had a city of 50,000+ residents, and the cities were within 20 miles of one another, they were placed within the same SMSA unless there was clear evidence that they should be separated. (This seems to have been the case in 1940 and 1950 as well, but the documentation for those years is not explicit.)
To be part of an SMSA, then, a county either had to contain the central city (or cities), or, as in 1940 and 1950, be considered metropolitan and integrated with the central city (or cities):
1. To be metropolitan, a county had to:
a. either contain 10,000 nonagricultural workers, or employ 10,000 nonagricultural workers, or contain at least one-tenth as many nonagricultural workers as the SMSA county with the largest city contained, or employ at least one-tenth as many nonagricultural workers as the SMSA county with the largest city employed, or contain 50+% of its population in minor civil divisions with a population density of 150+/square mile and contiguous with a central city, and,
b. have a labor force that was at least 75% nonagricultural.
1. For a county to be considered integrated with the central city:
a. 15+% of the workers residing in the county had to work in the county/counties containing the SMSA's central city/cities, or
b. 25+% of the workers employed in the county had to live in the county/counties containing the SMSA's central city/cities.
B. Like 1950 SMAs, 1970 New England SMSAs follow town and city (not county) boundaries. Furthermore, the 1970 census used a different criterion for metropolitan character in New England than the one used for the rest of the country; a town or city was considered metropolitan in New England if its population density was 100+/square mile.
1980
The 1980 SMSA definition is essentially the same as that for 1970, although one 1980 SMSA (Nassau-Suffolk, NY) had no proper central city.
1990
What were called SMAs in 1950, and SMSAs in 1970 and 1980, were referred to as "MAs"-Metropolitan Areas-in 1990. The concept in 1990 was virtually the same as in 1970 and 1980 and therefore very similar to the SMA idea of 1950. Conceptually, the 1990 MAs are further divided into:
1. Free-standing Metropolitan Statistical Areas (MSAs), which are generally surrounded by nonmetropolitan territory and therefore not integrated with other metropolitan areas, and
2. Primary Metropolitan Statistical Areas (PMSAs), which are the same as MSAs except that they are near, and economically/socially linked to, other PMSAs to form larger "CMSAs"-Consolidated Metropolitan Statistical Areas.