Union Members Technical Note
Last Modified Date: January 19, 2018
The estimates in this release are obtained from the Current Population Survey (CPS),
which provides basic information on the labor force, employment, and unemployment.
The survey is conducted monthly for the Bureau of Labor Statistics by the U.S. Census
Bureau from a scientifically selected national sample of about 60,000 eligible households.
The union membership and earnings data are tabulated from one-quarter of the CPS monthly
sample and are limited to wage and salary workers. All self-employed workers are excluded.
Beginning in January of each year, data reflect revised population controls used in the
CPS. Additional information about population controls is available on the BLS website at
Information in this release will be made available to sensory impaired individuals upon
request. Voice phone: (202) 691-5200; Federal Relay Service: (800) 877-8339.
Reliability of the estimates
Statistics based on the CPS are subject to both sampling and nonsampling error. When a
sample, rather than the entire population, is surveyed, there is a chance that the sample
estimates may differ from the true population values they represent. The exact difference,
or sampling error, varies depending on the particular sample selected, and this variability
is measured by the standard error of the estimate. There is about a 90-percent chance, or
level of confidence, that an estimate based on a sample will differ by no more than 1.6
standard errors from the true population value because of sampling error. BLS analyses are
generally conducted at the 90-percent level of confidence. The state section of this release
preserves the long-time practice of highlighting the direction of the movements in state
union membership rates and levels regardless of their statistical significance.
The CPS data also are affected by nonsampling error. Nonsampling error can occur for many
reasons, including the failure to sample a segment of the population, inability to obtain
information for all respondents in the sample, inability or unwillingness of respondents to
provide correct information, and errors made in the collection or processing of the data.
Information about the reliability of data from the CPS and guidance on estimating standard
errors is available at www.bls.gov/cps/documentation.htm#reliability.
Union membership questions
Employed wage and salary workers are classified as union members if they answer “yes” to
the following question: On this job, are you a member of a labor union or of an employee
association similar to a union? If the response is “no” to that question, then the interviewer
asks a second question: On this job, are you covered by a union or employee association
contract? If the response is “yes,” then these persons, along with those who responded “yes”
to being union members, are classified as represented by a union. If the response is “no”
to both the first and second questions, then they are classified as nonunion.
The principal definitions used in this release are described briefly below.
Union members. Data refer to members of a labor union or an employee association similar
to a union.
Union membership rate. Data refer to the proportion of total wage and salary workers who
are union members.
Represented by unions. Data refer to both union members and workers who report no union
affiliation but whose jobs are covered by a union or an employee association contract.
Nonunion. Data refer to workers who are neither members of a union nor represented by a
union on their job.
Usual weekly earnings. Data represent earnings before taxes and other deductions and
include any overtime pay, commissions, or tips usually received (at the main job in the
case of multiple jobholders). Prior to 1994, respondents were asked how much they usually
earned per week. Since January 1994, respondents have been asked to identify the easiest
way for them to report earnings (hourly, weekly, biweekly, twice monthly, monthly, annually,
other) and how much they usually earn in the reported time period. Earnings reported on a
basis other than weekly are converted to a weekly equivalent. The term "usual" is as perceived
by the respondent. If the respondent asks for a definition of usual, interviewers are instructed
to define the term as more than half of the weeks worked during the past 4 or 5 months.
Median earnings. The median is the amount which divides a given earnings distribution into
two equal groups, one having earnings above the median and the other having earnings below the
median. The estimating procedure places each reported or calculated weekly earnings value into
$50-wide intervals which are centered around multiples of $50. The actual value is estimated
through the linear interpolation of the interval in which the median lies.
Wage and salary workers. Workers who receive wages, salaries, commissions, tips, payment in
kind, or piece rates. The group includes employees in both the private and public sectors.
Union membership and earnings data exclude all self-employed workers, both those with
incorporated businesses as well as those with unincorporated businesses.
Full-time workers. Workers who usually work 35 hours or more per week at their sole or
Part-time workers. Workers who usually work fewer than 35 hours per week at their sole or
Hispanic or Latino ethnicity. Refers to persons who identified themselves in the enumeration
process as being Spanish, Hispanic, or Latino. Persons whose ethnicity is identified as Hispanic
or Latino may be of any race.