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A metropolitan area, or metro area, is a region consisting of a large urban core together with surrounding communities that have a high degree of economic and social integration with the urban core. For residents of metro areas, METAREA identifies the metro area of residence, contingent on varying delineations of metro areas across time and on variations in available geographic information and in confidentiality restrictions among samples.
Note: METAREA is not available for 2012-onward ACS and PRCS samples. To obtain metro area codes for these samples, see the MET2013 variable.
Metropolitan Area Delineations
Since 1950, the Bureau of the Budget (later renamed the Office of Management and Budget, or OMB), has produced and continually updated standard delineations of metropolitan areas for the U.S., defining each area as a county or a set of contiguous counties, or, for New England prior to 2003, as a set of cities or towns. In IPUMS samples for 1950 and later, the areas identified by METAREA generally correspond to contemporary OMB delineations, as were also used by the Census Bureau. For ACS samples through 2011, METAREA uses the 1999 OMB delineations, as were used for Census 2000 tabulations.
To delineate metro areas in pre-1950 samples, the general approach (used first by the creators of the 1940 PUMS and then by IPUMS for earlier samples) is to apply the 1950 OMB standards to historical statistics. One deviation from the 1950 standards is that all pre-1950 delineations are county-based, even in New England.
See the Comparability section for details on how delineations have changed over time and how confidentiality restrictions have affected METAREA's correspondence with standard delineations. For a listing of the counties associated with each metro area in each sample year, see the County Composition tables. For a complete record of OMB standards and changes since 1950, see the Census Bureau's historical delineations page.
User Caution: Incompletely Identified Metropolitan Areas
In the 1980 5% sample and all later samples, the populations of many metro areas are only partially identified by METAREA codes, and in many cases, the unidentified portion is considerably large. Users should consult the Incompletely Identified Metropolitan Areas page, which lists the percent of each metro area's population that resided in excluded areas for each sample.
The reason for incomplete coverage is that the source data for these samples include no specific information about metro areas. The most detailed geographic information available is for 1980 county groups or for 1990 or 2000 PUMAs, areas which occasionally straddle official metro area boundaries. If any portion of a straddling area's population resided outside a single metro area, the METAREA variable uses a conservative assignment strategy and identifies no metro area for all residents of the straddling area.
Users should not assume that the identified portion of a partly identified metro area is a representative sample of the entire metro area. In fact, because the unidentified population is located in areas that straddle the metro area boundaries, the identified population will often skew toward core populations and omit outlying communities. Also, weighted population counts for incompletely identified metro areas will be low by amounts ranging from 1 to 69% (since the unidentified individuals will not be counted as living in the metro area).
The METAREA Code System
METAREA codes are based primarily on the 4-digit OMB codes of 1990 metropolitan areas but with adjustments to reflect hierarchical relationships among metro areas across time. For any group of metro areas that were at any time defined to be components of a single metro area together, the 4-digit METAREA codes were adjusted to use the same first 3 digits. E.g., the METAREA code for Fort Worth, TX, is 1921, which indicates that the area was, in some sample, included as part of the Dallas-Fort Worth, TX, metro area, which has a code of 1920. Similarly, in cases where the 1990 OMB codes of disjoint areas share the same first 3 digits, the METAREA codes were adjusted to be distinct through 3 digits. This system enables users to obtain relatively consistent samples for "top-level" metro areas across time by grouping records according to the first 3 METAREA digits.
However, when IPUMS assigned METAREA codes for the 2000 and ACS samples, the codes were not adjusted to reflect any new splits or mergers. E.g., between 1990 and 1999, the OMB delineations merged the Odessa and Midland, TX, metro areas (with codes of 5800 and 5040) into a single area (with a code of 5800). Maintaining the hierarchical structure of METAREA codes would have required changing some existing 1990-based codes (e.g., changing the Midland code from 5040 to 5801), but in order to maintain static codes for prior users of METAREA, no codes were changed. Therefore, the first 3 digits of METAREA codes do not consistently represent top-level groups for the 2000 and ACS samples.
The METAREA Label System
METAREA labels are generally based on the OMB names of 1990 metropolitan areas or on the standard names of other older areas that do not appear in the 1990 delineations. A METAREA label may include the names of any major central cities that were ever included in the identified area, including some cities that are associated with a different code in some samples. E.g., the METAREA code 1920 has a label of "Dallas-Fort Worth, TX," but in most samples, records for Fort Worth have a code of 1921 and not 1920.
This system ensures that the first label in each 3-digit METAREA group will properly describe the full extent of the general 3-digit code group, but it also causes ambiguities for the detailed 4-digit codes. In samples where a city name appears in the labels for 2 different codes, users should assume that the city is associated only with the higher-numbered code.
Alternative for Pre-1950 Samples: Metropolitan Districts
Prior to the introduction of the OMB's standard metropolitan areas in 1950, the Census Bureau had defined and tabulated statistics for metropolitan districts, which differ from metropolitan areas primarily in their use of minor civil divisions (cities, towns, etc.) as building blocks instead of counties. The METDIST variable identifies metropolitan districts for pre-1950 samples using criteria similar to those used by the Census in 1940. One advantage of METDIST relative to METAREA is that METDIST was constructed for the 1940 sample after confidentiality requirements were lifted for 1940 and is therefore more complete than METAREA for that year.
Codes and Frequencies
Most of the changes in METAREA designations across samples correspond to official updates of metro area delineations. Such changes are meaningful for comparisons insofar as they correspond to real changes in metro area extents, and most do. But official delineations are built from relatively large, discretely-bounded areas (usually counties), and they change through discrete additions, subtractions, mergers, and divisions. In contrast, the "real" extents of metropolitan systems are fuzzy, varying by degrees, with no sharp boundaries, and their changes tend to be gradual. Therefore, all official changes in metro area delineations are, to some extent, arbitrary, with potentially misleading effects on measures of population change within metro areas.
Before interpreting any observed changes in population characteristics by METAREA, users should consult the County Composition tables to determine whether there have been any changes in a metro area's delineation. Where changes have occurred, users should consider to what extent the changes may have affected population size and composition. This is especially important in cases where two or more similarly sized population centers have at different times been included, and not included, in the same metro area (e.g., San Francisco and Oakland, CA; Odessa and Midland, TX; etc.).
A second significant complication for METAREA comparability is that, due to variations in confidentiality restrictions and in the geographic information available in public use samples, it is not possible to identify all residents of all metro areas in all samples, and these restrictions affect the representativeness of METAREA to varying degrees across samples and even among metro areas within samples. Most problematically, as noted in the Description section, the populations of many metro areas are only partially identified by METAREA in 1980 and later samples. Users of these samples should consult the Incompletely Identified Metropolitan Areas page to find the percent of each metro area's population that is excluded by METAREA codes for each sample.
The remainder of this section details how standards and restrictions vary across samples. Despite the many adjustments in official terminology and criteria noted below, the general concept of "metropolitan areas" that official delineations are intended to represent has remained essentially the same. As stated in the Census Bureau's Geographic Areas Reference Manual, p. 13-5, "Most of the changes in the standards have been minor and have not reflected signficant deviations from the concepts underlying the standards used for the 1950 census."
OMB standards have used different terms to describe metro areas at different times:
- In 1950, the term was Standard Metropolitan Area (SMA).
- From 1960 through 1981, the term was Standard Metropolitan Statistical Area (SMSA).
- From 1983 through Census 2000, the term was Metropolitan Area (MA), which included free-standing Metropolitan Statistical Areas (MSAs), and Primary Metropolitan Statistical Areas (PMSAs), which grouped together form larger Consolidated Metropolitan Statistical Areas (CMSAs).
- With the 2003 definitions, the OMB established a more comprehensive concept of Core Based Statistical Areas (CBSAs), which include Metropolitan Statistical Areas and smaller Micropolitan Statistical Areas.
- Micropolitan Statistical Areas, which have an urban core of between 10,000 and 50,000 persons in size, are generally too small to be identified in public use microdata.
- The new Metropolitan Statistical Areas correspond in concept to the metropolitan areas of earlier standards, but they use a new code system and are entirely county-based (unlike earlier standards that based New England areas on towns and cities). For these reasons, among others, METAREA has not been extended to use the latest OMB standards. Users interested in obtaining codes for 2013 MSAs should see MET2013.
In 1950, an SMA is a county or group of contiguous counties (or county equivalents) that 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.
- To be considered metropolitan in character, a county had to
- either contain 10,000 nonagricultural workers, or 10 percent of the nonagricultural workers working in the SMA, or contain 50+ percent of its population in minor civil divisions that had a population density of 150+/square mile and were contiguous with the central city, and
- have at least 2/3 of its employed residents working in nonagricultural occupations.
- Criteria for integration with a central city include situations where:
- 15+ percent of the workers residing in the county worked in the county which contained the SMA's largest city, or
- 25+ percent of the workers employed in the county lived in the county which contained the SMA's largest city, or
- 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.
For 1940 1% and 1950, SMAs are identified in METAREA only if the following confidentiality criteria are met:
- The SMA's 1980 population must be 100,000+.
- The state's non-metropolitan population must be at least 100,000 in 1980.
- 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 defined but are not identified for this reason.)
- For SMAs that crossed state lines, the 100,000+ population threshold was applied to each state's portion of that SMA. If the portion within a particular state exceeded 100,000 residents, the SMA could be identified; if not, it remained confidential. Thus, some interstate SMAs are only partially identifiable.
There were two types of exceptions to these rules in the 1940 1% and 1950 samples:
- While the original 1940 PUMS identified the same set of metropolitan areas as the 1950 PUMS, the IPUMS suppresses those 1940 METAREAs that did not meet the requisite criteria for metropolitan status at that time (and codes them as non-metropolitan in the METRO variable as well). The following METAREAs were identified in the 1940 PUMS but are not identified in the IPUMS for 1940:
|Albuquerque, NM||Muncie, IN|
|Baton Rouge, LA||Ogden, UT|
|Bay City, MI||Orlando, FL|
|Green Bay, WI||Pittsfield, MA|
|Greenville, SC||Raleigh, NC|
|Honolulu, HI||San Bernadino, CA|
|Lorain-Elyria, OH||Sioux Falls, SD|
|Lubbock, TX||Wichita Falls, TX|