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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 Bureau of 

Labor Statistics 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, 

with appropriate credit, may be reproduced without 

permission. This information is available to 

sensory-impaired individuals on request. Voice 

phone: (202) 691-5200; TDD message referral 

phone number: 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 are generally 

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/eetech_methods.pdf. 

Concepts and Definitions 

Concepts used in this report are defined below. 

Civilian noninstitutional population. Included are 

persons 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 

persons 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. Persons 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. 
97 

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 the race of 

persons. Persons 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 persons 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 

persons who identified themselves in the survey as 

being Spanish, Hispanic, or Latino. Persons whose 

ethnicity is identified as Hispanic or Latino may be 

of any race. 

Family. A family is a group of two or more persons 

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. 

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 selfemployed category. Self-employed persons whose 

businesses are incorporated are included in wage 

and salary employment. 

Wage and salary workers. These are workers who 

receive wages, salaries, commissions, tips, payment 

in kind, or piece rates. The group includes 

employees in both the private and public sectors 

but, for purposes of the earnings series, excludes all 

self-employed persons, regardless of whether their 

businesses are incorporated. 

Hourly paid workers. Workers who are paid an 

hourly wage are a subset of wage and salary 

workers, representing approximately three-fifths of 

all wage and salary workers. Workers paid by the 

hour are, therefore, included in the estimates of 

median usual weekly earnings in this report, along 

with salaried workers and other workers not paid by 

the hour. Data for workers paid at hourly rates are 

presented separately in Table 26. 

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, 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.” 

Medians of usual 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-yearolds 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, $250, $300, or $400. 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. Medians, for 
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example, measure the central tendency of a 

multipeaked distribution that shifts over time. As 

the 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 short-term changes in 

the medians, as well as in ratios of the medians. 

Hours at work. These are the actual hours worked 

(at all jobs) during the reference week. For 

example, persons who normally work 40 hours a 

week but were off during the Columbus Day 

holiday would be reported as working 32 hours, 

even though they were paid for the holiday. 

Usual hours, or usual full- or part-time status. 

Data on persons “at work” exclude persons 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 persons 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, persons also are 

classified according to their usual full- or part-time 

status. In this context, full-time workers are those 

who usually worked 35 hours or more (at all jobs 

combined). This group includes some individuals 

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 individuals 

who actually worked more than 34 hours in the 

reference week, as well as those who were 

temporarily absent from work. 

Occupation and industry. This information applies 

to the job held during the reference week. Persons 

with two or more jobs are classified in the 

occupation and industry at which they worked the 

greatest number of hours. The occupational and 

industry classification of CPS data is based on the 

2002 Census Bureau occupational and industrial 

classification systems, which are derived from the 

2000 Standard Occupation Classification (SOC) 

and the 2002 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 

persons 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 persons 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.