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Glossary of terms

This glossary defines terms related to the economy and the job market.
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Mass Layoff Statistics (MLS)

A federal/state cooperative effort to identify, describe and track the effects of major job cutbacks using each state’s unemployment insurance database. The program tracks reports on mass layoff actions (50 people or more filing initial unemployment claims) that result in workers being separated from their jobs for five weeks or longer. These MLS reports were discontinued in June 2013. (


See average.

Measurement error

The difference between the actual value and measured value of a quantity.


The midpoint in a sequential data set where half of the numbers lie above and half lie below.

Metropolitan division

Metropolitan statistical areas containing a single core with a population of 2.5 million or more (as well as meeting other criteria) may be subdivided into metropolitan divisions. In Washington state, the Seattle-Tacoma-Bellevue MSA is subdivided into two metropolitan divisions: the Seattle-Bellevue-Everett MD (which consists of King and Snohomish Counties) and the Tacoma MD (which consists of Pierce County).

Metropolitan statistical area

A geographic entity for use by federal statistical agencies. A metropolitan statistical area consists of at least one urbanized area with a population of 50,000 or more, along with adjacent counties with a high degree of social and economic integration demonstrated by worker commute patterns.

Micropolitan statistical area

A geographic entity for use by federal statistical agencies. A micropolitan statistical area is an urban cluster that has a population of at least 10,000 but less than 50,000 people, comprised of a core central county or counties. This includes adjacent counties with social and economic ties demonstrated by worker commute patterns.

Migrant agricultural worker

A person employed in agricultural work of a seasonal or temporary nature who is required to be absent overnight from his or her permanent place of residence. Exceptions are immediate family members of agricultural employers, farm labor contractors and temporary foreign workers. Temporary foreign workers are nonimmigrant aliens authorized to work in agricultural employment for a specified time period, normally less than a year.


The number that appears the most frequently in a distribution of numbers.