Technical Note
The estimates in this release are based on annual average data obtained from
the Current Population Survey (CPS). The CPS is a monthly survey of about 60,000
eligible households that is conducted by the U.S. Census Bureau for the Bureau of
Labor Statistics (BLS).
Questions were added to the CPS in June 2008 to identify persons with a
disability in the civilian noninstitutional population age 16 and older. The
addition of these questions allowed the BLS to begin releasing monthly labor
force data from the CPS for persons with a disability. The collection of these
data is sponsored by the Department of Labor's Office of Disability Employment
Policy.
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 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.
A full discussion of the reliability of data from the CPS and information on
estimating standard errors is available online at
www.bls.gov/cps/documentation.htm#reliability.
CPS estimates are controlled to population totals that are available by age, sex,
race, and Hispanic ethnicity. These controls are developed by the Census Bureau and
are based on complete population counts obtained in the decennial census. In the
years between decennial censuses, they incorporate the latest information about
population change (births, deaths, and net international migration). As part of its
annual update of population estimates, the Census Bureau introduces adjustments to
the total population controls. The estimated effect of the new controls on CPS data
for 2011 (based on a comparison of December 2010 data on the old and new controls)
was to decrease the total employment level by 472,000. The number of employed persons
with a disability was lower by 11,000 and the number with no disability was lower by
461,000; these effects reflect an indirect adjustment related to changes in population
size and composition by age, sex, race, and Hispanic ethnicity. The updated controls
had a negligible impact on unemployment rates and other ratios. (The estimates of the
population of persons with a disability are not controlled to independent population
totals of persons with a disability because such data are not currently available.
Without independent population totals, sample-based estimates are more apt to vary
from one time period to the next.) Additional information is available on the BLS Web
site at www.bls.gov/cps/documentation.htm#pop.
Disability questions and concepts
The CPS uses a set of six questions to identify persons with disabilities. In the
CPS, persons are classified as having a disability if there is a response of "yes" to
any of these questions. The disability questions appear in the CPS in the following
format:
This month we want to learn about people who have physical, mental, or emotional
conditions that cause serious difficulty with their daily activities. Please answer
for household members who are 15 years and older.
--Is anyone deaf or does anyone have serious difficulty hearing?
--Is anyone blind or does anyone have serious difficulty seeing even when
wearing glasses?
--Because of a physical, mental, or emotional condition, does anyone have
serious difficulty concentrating, remembering, or making decisions?
--Does anyone have serious difficulty walking or climbing stairs?
--Does anyone have difficulty dressing or bathing?
--Because of a physical, mental, or emotional condition, does anyone have
difficulty doing errands alone such as visiting a doctor's office or
shopping?
The CPS questions for identifying individuals with disabilities are only asked of
household members who are age 15 and older. Each of the questions ask the respondent
whether anyone in the household has the condition described, and if the respondent
replies "yes," they are then asked to identify everyone in the household who has the
condition. Labor force measures from the CPS are tabulated for persons age 16 and older.
More information on the disability questions and the limitations of the CPS disability
data is available on the BLS Web site at www.bls.gov/cps/cpsdisability_faq.htm.
Other definitions
Other definitions used in this release are described briefly below. Additional
information on the concepts and methodology of the CPS is available at
www.bls.gov/cps/documentation.htm.
Employed persons are all those who, during the survey reference week (which is
generally the week including the 12th day of the month), (a) did any work at all as
paid employees; (b) worked in their own business, profession, or on their own farm;
(c) worked 15 hours or more as unpaid workers in a family-operated enterprise; or
(d) were temporarily absent from their jobs because of illness, vacation, labor
dispute, or another reason.
Unemployed persons are all persons who had no employment during the reference week,
were available for work, except for temporary illness, and had made specific efforts
to find employment sometime during the 4 weeks preceding the survey. Persons who were
waiting to be recalled to a job from which they had been laid off need not have been
looking for work to be classified as unemployed.
Civilian labor force comprises all persons classified as employed or unemployed.
Unemployment rate represents the number of unemployed persons as a percent of the
civilian labor force.
Not in the labor force includes all persons who are not classified as employed or
unemployed. Information is collected on their desire for and availability to take a
job at the time of the CPS interview, job search activity in the prior year, and
reason for not looking in the 4-week period prior to the survey week. This group
includes individuals marginally attached to the labor force, defined as persons
not in the labor force who want and are available for a job and who have looked for
work sometime in the past 12 months (or since the end of their last job if they held
one within the past 12 months). They are not counted as unemployed because they had
not actively searched for work in the prior 4 weeks. Within the marginally attached
group are discouraged workers--persons who are not currently looking for work because
they believe there are no jobs available or there are none for which they would qualify.
The other persons marginally attached to the labor force group includes persons who want
a job but had not looked for work in the past 4 weeks for reasons such as family
responsibilities or transportation problems.
At work part time for economic reasons, a measure sometimes referred to as involuntary
part time, refers to individuals who gave an economic reason for working 1 to 34 hours
during the reference week. Economic reasons include slack work or unfavorable business
conditions, inability to find full-time work, and seasonal declines in demand. Those who
usually work part time must also indicate that they want and are available for full-time
work.
Occupation, industry, and class of worker for the employed relate to the job held in
the survey reference week. Persons with two or more jobs are classified in the job at
which they worked the greatest number of hours. Persons are classified using the 2010
Census occupational and 2007 Census industry classification systems. The class-of-worker
breakdown assigns workers to the following categories: Private and government wage and
salary workers, self-employed workers, and unpaid family workers. Wage and salary workers
receive wages, salary, commissions, tips, or pay in kind from a private employer or from
a government unit. Self-employed persons are those who work for profit or fees in their
own business, profession, trade, or farm. Only the unincorporated self-employed are
included in the self-employed category. Self-employed persons who respond that their
businesses are incorporated are included among wage and salary workers.
