For directions on reading the variable description see Data Dictionary Introduction.

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1850	1860	1870	1880	1900	1910	1920	1940	1950	1960	1970	1980	1990
X	X	X	X	X	X	X	X	X		M	S,M	X

Universe: 
1850 - 1950: All households and group quarters. 
1970:            All households and group quarters in Metro samples. 
1980:            All households and group quarters in State and Metro samples. 
1990:            All households and group quarters. 

Codes and Frequencies - Detailed

Description: 
Metropolitan areas are counties or combinations of counties centering on a substantial urban area. METAREA identifies the household's metropolitan area of enumeration if the household was located in a metropolitan area large enough to meet confidentiality requirements. 

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.

• 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.

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. For further information, see our discussion of geographic concepts in Chapter 1, "Introduction."

In the IPUMS, metropolitan areas are listed according to their 1990 definition and given a five digit code. Because of changes in the county composition of metropolitan areas over time, however, the 1990 coding system had to be modified somewhat. In general, metropolitan areas that are part of a CMSA in 1990 are listed independently of the CMSA. However, if the county components of a metropolitan area were part of another during some years, then this metropolitan area is listed under the appropriate CMSA with a detail code. For example, Gary, Indiana is a metropolitan area whose counties were part of the Chicago metropolitan area in 1940-50. Therefore, Gary is coded under the CMSA "Chicago-Gary-Lake" with a detail code. Conversely, Ann Arbor is part of the CMSA "Detroit-Ann Arbor" in 1990. Washtenaw County, which contains the metropolitan area Ann Arbor, was in all years separately identifiable from Detroit. Therefore, Ann Arbor is coded separately from Detroit. Researchers will need to consult the table listing metropolitan area county composition across all census years. A complete list of the metropolitan areas that make up each CMSA is also available. (See "Geographic Tools" in Volume 2: User's Guide Supplement for both of these tables.) 

There is some variable description confusion for Boston, Brockton, Providence, and New York. After 1940-1950, metropolitan area county descriptions include parts of counties. In the Northeast, it is difficult to determine absolutely when some metropolitan areas separated from CMSAs. Researchers interested in these areas should consult a map. 

1950 and Pre-1950 SAMPLES 

A. In 1950, an SMA is a county or group of contiguous counties which contained at least one city of 50,000+ residents. To be part of an SMA, a county either had to contain the 50,000+ city, or had to be metropolitan in character and integrated with a central city. 

1. To be considered metropolitan in character, a county had to
1. either contain 10,000 nonagricultural workers, or 10% of the nonagricultural workers working in the SMA, or contain 50+% of its population in minor civil divisions with a population density of 150+/square mile and contiguous with the central city, and
2. have at least 2/3 of its employed residents working in nonagricultural occupations.
2. Criteria for integration with a central city include situations where:
1. 15+% of the workers residing in the county worked in the county which contained the SMA's largest city, or
2. 25+% of the workers employed in the county lived in the county which contained the SMA's largest city, or
3. the monthly total of phone calls from the county to the county which contained the SMA's largest city was 4+ times as large as the county's number of phone subscribers.

C. For 1940 and 1950, SMAs are identified only if the following confidentiality criteria are met: 

1. The SMA's 1980 population must be 100,000+.
2. The state's nonmetropolitan population was at least 100,000 in 1980.
3. The state's total non-identifiable population (resulting from the two previous rules) must be either zero or 100,000+ in 1980. (Four SMAs are not identified for this reason.)
4. For interstate SMAs, the three previous rules were applied to each state's portion. If the portion within a particular state exceeded 100,000 residents, it could be identified; if not, it remained confidential. Thus, some interstate SMAs are only partially identifiable.

1. To be considered metropolitan in character, a county had to
1. either contain 10,000 nonagricultural laborers, or the number of nonagricultural laborers is at least 10% as large as the number of nonagricultural laborers working in the primary county of the SMA, or contain 50+% of its population in minor civil divisions with a population density of 150+ persons per square mile and contiguous to the central city, and
2. have at least 2/3 of its employed residents working in nonagricultural occupations.
2. For 1850 to 1920 the criterion for integration with the central city was that at least 25% of the county population resided in the Metropolitan District of the central city.

A. 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 PUMS 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:
1. 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,
2. have a labor force that was at least 75% nonagricultural.
2. For a county to be considered integrated with the central city:
1. 15+% of the workers residing in the county had to work in the county/counties containing the SMSA's central city/cities, or
2. 25+% of the workers employed in the county had to live in the county/counties containing the SMSA's central city/cities.

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. SMSAs with fewer than 100,000 residents are not identified for confidentiality reasons. The 1980 State sample dentifies only the 180 qualifying SMSAs that do not cross state lines. The 1980 Metro sample identifies all 282 qualifying SMSAs and codes the 36 remaining SMSAs into 18 SMSA pairs, each with a combined population of 100,000+. The pairing allows all metropolitan territory to be identified without violating confidentiality requirements. Each pair shares a common code as follows: 

• Bangor, ME and Lewiston-Auburn, ME 
• Tioga County, NY (part of the Binghampton, NY/PA SMSA) and Elmira, NY 
• Bismark, ND and Grand Forks, ND/MN 
• Bloomington, IN and Owensboro, KY 
• Bristol, CT and Meriden, CT 
• Bryan-College Station, TX and Sherman-Dennison, TX 
• Guilford County, NC (excluding Greensboro city and High Point city; the entire county is part of the Greensboro-Winston-Salem-High Point, NC SMSA) and Burlington, NC 
• Casper, WY and Great Falls, MT 
• Dubuque, IA and Iowa City, IA 
• El Paso, TX (excluding El Paso city) and Las Cruces, NM 
• Lawton, OK and Enid, OK 
• Fitchburg-Leominster, MA and Pittsfield, MA 
• Fort Walton Beach, FL and Panama City, FL 
• La Crosse, WI and Rochester, MN 
• Laredo, TX and Victoria, TX 
• Topeka, KS (excluding Topeka City) and Lawrence, KS 
• Saline County, AR (part of Little Rock-N. Little Rock, AR SMSA) and Pine Bluff, AR 
• Midland, TX and San Angelo, TX 

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.

1. The same list of Metropolitan Areas were identified in the 1940 and 1950 PUMS, though some did not meet metropolitan criteria in the earlier census year. The IPUMS suppresses these 1940 metropolitan area codes (and codes them non-metropolitan in the METRO variable as well), but these locales can still be identified using the SEA variable. The following METAREAs are not identifiable in the IPUMS 1940 sample: