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Technical Note

The estimates in this report were obtained from the 

Current Population Survey (CPS), a national monthly 

sample survey of approximately 60,000 households, 

which provides a wide range of information on the labor 

force, employment, and unemployment. Earnings and union 

affiliation data are collected from one-fourth of the CPS 

monthly sample. The survey is conducted for the U.S. Bureau 

of Labor Statistics (BLS) by the U.S. Census Bureau, using 

a scientifically selected national sample with coverage in all 

50 States and the District of Columbia.

Material in this report is in the public domain and may be 

reproduced without permission. This information is available 

to sensory-impaired individuals on request. Voice phone: 

(202) 691-5200; Federal Relay Service: 1-800-877-8339.

Reliability of the Estimates

Statistics based on the CPS are subject to both sampling and 

nonsampling error. When a sample, rather than an 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 generally are conducted at 

the 90-percent level of confidence.

All other types of error are referred to as 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 data. CPS data also are affected by nonsampling 

error. The full extent of nonsampling error is unknown, but 

special studies have been conducted to quantify some sources 

of such error in the CPS. For further discussion of the reliability of data from the CPS and information on estimating 

standard errors, see the Household Data technical documentation provided at http://www.bls.gov/cps/documentation.

htm#reliability.

Concepts and Definitions

Concepts used in this report are defined below.

Civilian noninstitutional population. The civilian noninstitutional population includes people 16 years of age and 

older residing in the 50 States and the District of Columbia who are not confined to institutions (for example, 

correctional facilities and residential nursing and mental 

health care facilities) and who are not on active duty in 

the Armed Forces.

Civilian labor force. This group comprises all people classified as employed or unemployed.

Employed persons. Employed persons are those who, during 

the survey week, (a) did any work at all as paid civilians; (b) 

worked in their own business or profession or on their own 

farm; (c) worked 15 hours or more as unpaid workers in a 

family business; or (d) were temporarily absent from their jobs 

because of illness, vacation, bad weather, or another reason.

Unemployed persons. Unemployed persons are those who 

had no employment during the survey week, were available 

for work at that time, and made specific efforts to find employment sometime in the prior 4 weeks. Workers laid off 

from their former jobs and awaiting recall did not need to be 

looking for work to be classified as unemployed.

Civilian labor force participation rate. This rate is the civilian labor force as a percent of the civilian noninstitutional 

population.

Employment-population ratio. This ratio represents the 

proportion of the population that is employed.

Unemployment rate. This rate represents the number of 

unemployed persons as a percent of the civilian labor force.

Race. White, Black or African American, and Asian are terms 

used to describe race. People in these categories are those 

who selected that race group only. Data for the remaining 

race categories—American Indian or Alaska Native, Native 

Hawaiian or Other Pacific Islanders, and people who selected 

more than one race category—are included in totals but are 

not shown separately because the number of survey respondents was too small to develop estimates of sufficient quality 

for publication. In the survey process, race is determined by 

the household respondent.

Hispanic or Latino ethnicity. This term refers to people 

who identified themselves in the survey as being Spanish, 
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Hispanic, or Latino. People whose ethnicity is identified as 

Hispanic or Latino may be of any race.

Family. A family is a group of two or more people residing 

together who are related by birth, marriage, or adoption. 

Families are classified either as married-couple families or 

as families maintained by women or men without spouses. 

Families include those with children under 18 in the home 

and those without children under 18.

Self-employed workers. Self-employed workers are those 

who work for profit or fees in their own business, profession, 

trade, or farm. Unincorporated self-employed are included in 

the self-employed category. Self-employed workers whose 

businesses are incorporated are included with wage and 

salary workers.

Wage and salary workers. These are workers who receive 

wages, salaries, commissions, tips, payment in kind, or piece 

rates. This includes employees in both the private and public 

sectors. Union membership and earnings data of wage and 

salary workers exclude all self-employed workers, both those 

with incorporated businesses and those with unincorporated 

businesses.

Hourly paid workers. Workers who are paid an hourly wage 

are a subset of wage and salary workers. Historically, workers 

paid an hourly wage have made up approximately three-fifths 

of all wage and salary workers. Estimates of median usual 

weekly earnings in this report are based on the earnings of 

all workers—those paid by the hour and those paid a salary 

or on some other basis.

Usual weekly earnings. Data are collected on wages and 

salaries before taxes and other deductions and include any 

overtime pay, commissions, or tips usually received (at the 

principal job in the case of multiple jobholders). Earnings of 

self-employed workers are excluded, regardless of whether 

their businesses are incorporated. Prior to 1994, respondents 

were asked to report earnings 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, or other) and how much they 

usually earn in the reported 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 the weeks 

worked during the past 4 or 5 months.”

Median weekly earnings. The median is the amount that 

divides a given earnings distribution into two equal groups: 

one having earnings above the median and the other having 

earnings below the median. The BLS estimating procedure 

for determining the median of an earnings distribution places 

each reported or calculated weekly earnings value into a 

$50-wide interval that is centered on a multiple of $50. The 

value of the median is estimated through a linear interpolation of the interval in which the median lies. Over-the-year 

changes in the medians for specific groups may not necessarily be consistent with the movements estimated for the 

overall group boundary. The most common reasons for this 

possible anomaly follow: (1) There could be a change in the 

relative weights of the subgroups. For example, the medians 

of both 16- to 24-year-olds and those 25 years and over may 

rise, but if the lower earning 16-to-24 age group accounts 

for a greatly increased share of the total, the overall median 

could actually fall. (2) There could be a large change in the 

shape of the distribution of reported earnings. This could be 

caused by survey observations that are clustered at rounded 

values, for example, $300, $400, or $500. An estimate lying 

in a $50-wide centered interval containing such a cluster, or 

“spike,” tends to change more slowly than one in other intervals. Consider, for example, the calculation of the median 

for a multipeaked distribution that shifts over time. As such 

a distribution shifts, the median does not necessarily move 

at the same rate. Specifically, the median takes relatively 

more time to move through a frequently reported interval but, 

once above the upper limit of such an interval, it can move 

relatively quickly to the next frequently reported earnings 

interval. BLS procedures for estimating medians mitigate 

such irregular movements of the measures; however, users 

should be cautious of these effects when evaluating shortterm changes in the medians, and in ratios of the medians.

Hours at work. These are the actual hours worked (at all 

jobs) during the survey reference week. For example, people 

who normally work 40 hours a week but were off during the 

Columbus Day holiday would be reported as working 32 

hours, even if they were paid for the holiday.

Usual hours, or usual full- or part-time status. Data on people 

“at work” exclude those who were temporarily absent from 

a job and therefore classified in the zero-hours worked category, “with a job but not at work.” These are workers who 

were absent from their jobs for the entire week for reasons 

such as bad weather, vacation, illness, or involvement in a 

labor dispute. To differentiate a person’s normal schedule 

from his or her activity during the reference week, workers 

also are classified according to their usual full- or part-time 

status. In this context, full-time workers are those who usually work 35 hours or more (at all jobs combined) per week. 

This group includes workers who worked less than 35 hours 

in the reference week for either economic or noneconomic 

reasons and those who were temporarily absent from work. 

Similarly, part-time workers are those who usually work less 

than 35 hours per week (at all jobs), regardless of the number 

of hours worked in the reference week. This may include 

some people who actually worked more than 34 hours in 

the reference week, as well as those who were temporarily 

absent from work.
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Occupation and industry. This information applies to the job 

held during the reference week. People with two or more jobs 

are classified in the occupation and industry in which they 

worked the greatest number of hours. The occupational 

and industry classification of CPS data is based on the 

2002 Census Occupational Classification system and the 

2007 Census Industrial Classification system, which are 

derived from the 2000 Standard Occupation Classification (SOC) and the 2007 North American Industry 

Classification (NAICS). Additional information about 

these classifications is available online at http://www.

bls.gov/cps/cpsoccind.htm.

Work experience. These data reflect work activity during the 

calendar year and are obtained from the Annual Social and 

Economic Supplement (ASEC) to the Current Population 

Survey. Estimates of people who worked were based on 

“yes” responses to the following questions in the ASEC: 

“Did you work at a job or business at any time during [the 

survey reference year]?” or “Did you do any temporary, 

part-time, or seasonal work even for a few days during 

[the survey reference year]?” Since the reference period is 

a full year, the number of people with some employment 

or unemployment greatly exceeds the average levels for 

any given month, which are based on a 1-week reference 

period, and the corresponding annual averages of monthly 

estimates.

Poverty classification. Poverty statistics presented in this 

report are based on definitions developed by the Social 

Security Administration in 1964 and revised by the Federal 

interagency committees in 1969 and 1981. These definitions 

originally were based on the Department of Agriculture’s 

Economy Food Plan and reflected the different consumption 

requirements of families, based on factors such as family size 

and the number of children under 18 years of age. The actual 

poverty thresholds vary in accordance with the makeup of the 

family. Poverty thresholds are updated each year to reflect 

changes in the Consumer Price Index for All Urban Consumers (CPI-U). The thresholds do not vary geographically. For 

more information on poverty data and thresholds, see http://

www.census.gov/hhes/www/poverty/poverty.html.