Description

LMA is an unrecoded variable that identifies the labor market area of enumerated households.

Labor market areas (LMAs) are groups of counties with a combined population of 100,000+ residents. The county composition of LMAs is based on a hierarchical cluster analysis of journey-to-work data that defines county-to-county commuter flows. All U.S. counties or county equivalents are classified in an LMA, and the boundaries of the LMA may contain counties from more than one state. In 1980, there are 382 labor market areas; in 1990, there are 394 LMAs.

The hierarchical cluster analysis uses an algorithm to identify groups of counties with strong commuting ties and organizes spatial commuting zones based on the calculated cluster centroid distances. (See C. Tolbert and M. Sizer, U.S. Commuting Zones and Labor Market Areas, for additional information on the statistical techniques used to construct commuting zones and LMAs.) When necessary, commuting zones are aggregated to meet the minimum 100,000 total population criteria set by the Census Bureau to protect confidentiality. (See COMZONE for additional information.) LMAs vary in total population size from 100,000 to several million, without a maximum population size restriction.

This variable is only available for the 1980 and 1990 Labor Market Area samples. LMA is a 3-digit un-recoded numeric variable which identifies the labor market area of enumerated households. Labor market areas (LMAs) are groups of counties with a combined population of 100,000+ residents. The county composition of LMAs is based on a hierarchical cluster analysis of journey-to-work data that defines county-to-county commuter flows. All U.S. counties or county equivalents are classified in an LMA, and the boundaries of the LMA may contain counties from more than one state. In 1980, there are 382 labor market areas; in 1990, there are 394 LMAs (See Description for a detailed discussion on the construction of LMAs.). LMA specific variable codes for missing, edited, or unidentified observations, observations not applicable (N/A), observations not in universe (NIU), top and bottom value coding, etc. are provided below if applicable by Census year (and data sample if specified).

LMA Specific Variable Codes
See links below for detailed Labor Market Area codes:
1980 Labor Market Area composition
1990 Labor Market Area composition

Comparability

LMAs are constructed via the same process in 1980 and 1990, but the coding and composition of LMAs are not comparable across years for individual-level PUMS data. Using county-level summary data, researchers can examine compositional changes in LMAs; however, the individual-level data released for the labor market samples of the 1980 and 1990 PUMS identify LMA and commuting zones only, not the constituent counties. Since many of the 1990 LMAs contain counties that clustered differently in the 1980 LMAs, it is not possible to determine which fraction of individual-level data in the 1980 LMA would cluster in the 1990 LMA. For this reason, the IPUMS program does not attempt to harmonize the 1980 and 1990 LMA codes but leaves the codes at their 1980 and 1990 values.

For other samples from the post-1950 period, the Census Bureau designated different geographic entities to meet confidentiality requirements. These include 1970 county groups of 250,000+ population (in CNTYGP97), 1980 county groups of 100,000+ population (in CNTYGP98), 1990 Public Use Microdata Areas (PUMAs) of 100,000+ population (in PUMA), Public Use Microdata Areas (PUMAs) of 100,000+ population for the 5 percent sample of the 2000 census (in PUMA), and Super-Public Use Microdata Areas (Super-PUMAs) of 400,000+ population for the 1 percent sample of the 2000 census (in PUMASUPR).

Universe

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• 1990: 0.5% LMA
• 1980: 1% LMA
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Flags

Editing Procedure

There is no editing procedure available for this variable.