but not at work are excluded from the hours distributions and the computations of average hours. In the payroll survey, employees on paid vacation, paid holiday, or paid sick leave are included and assigned the number of hours for which they were paid during the reporting period.

period. There are also wide differences in sampling techniques and collecting and estimating methods, which cannot be readily measured in terms of impact on differences in level and trend of the two series.

COMPARABILITY OF THE HOUSEHOLD DATA WITH OTHER SERIES

Unemployment insurance data. The unemployed total from the household survey includes all persons who did not have a job at all during the survey week and were looking for work or were waiting to be called back to a job from which they had been laid off, regardless of whether or not they were eligible for unemployment insurance. Figures on unemployment insurance claims, prepared by the Manpower Administration of the Department of Labor, exclude persons who have exhausted their benefit rights, new workers who have not earned rights to unemployment insurance, and persons losing jobs not covered by unemployment insurance systems (agriculture, some State and local government, domestic service, self-employment, unpaid family work, and religious organizations).

In addition, the qualifications for drawing unemployment compensation differ from the definition of unemployment used in the household survey. For example, persons with a job but not at work and persons working only a few hours during the week are sometimes eligible for unemployment compensation but are classified as employed rather than unemployed in the household survey.

For an examination of the similarities and differences between State insured unemployment and total unemployment, see "Measuring Total and State Insured Unemployment" by Gloria P. Green in the June 1971 issue of the Monthly Labor Review. Reprints of this article may be obtained upon request.

Agricultural employment estimates of the Department of Agriculture. The principal differences in coverage are the inclusion of persons under 16 in the Statistical Research Service (SRS) series and the treatment of dual jobholders who are counted more than

COMPARABILITY OF THE PAYROLL EMPLOYMENT DATA WITH OTHER SERIES

Statistics on manufactures and business, Bureau of the Census. BLS establishment statistics on employment differ from employment counts derived by the Bureau of the Census from its censuses or annual sample surveys of manufacturing establishments and the censuses of business establishments. The major reasons for some noncomparability are different treatment of business units considered parts of an establishment, such as central administrative offices and auxiliary units, the industrial classification of establishments, and different reporting patterns by multiunit companies. There are also differences in the scope of the industries covered, e.g., the Census of Business excludes professional services, public utilities, and financial establishments, whereas these are included in BLS statistics.

County Business Patterns. Data in County Business Patterns (CBP), published jointly by the U.S. Departments of Commerce and Health, Education, and Welfare, differ from BLS establishment statistics in the treatment of central administrative offices and auxiliary units. Differences may also arise because of industrial classification and reporting practices. In addition, CBP excludes interstate railroads and government, and coverage is incomplete for some of the nonprofit activities.

Employment covered by State unemployment insurance programs. Most nonagricultural wage and salary workers are covered by the unemployment insurance programs. Beginning in January 1972, coverage was expanded to include employees of small firms and selected nonprofit activities who had not been covered previously. However, certain activities, such as interstate railroads, parochial schools, churches and most State and local government activities are not covered by unemployment insurance whereas these are included in BLS establishment statistics.

COLLECTION AND COVERAGE

Statistics on the employment status of the population, the personal, occupational, and other characteristics of the employed, the unemployed, and persons not in the labor force, and related data are compiled for the BLS by the Bureau of the Census in its Current Population Survey (CPS). A detailed description of this survey appears in Concepts and Methods Used in Manpower Statistics from the Current Population Survey, BLS Report 313. This report is available from BLS on request.

These monthly surveys of the population are conducted with a scientifically selected sample designed to represent the civilian noninstitutional population. Respondents are interviewed to

obtain information about the employment status of each member of the household 16 years of age and over. Separate statistics are also collected and published for 14 and 15 year olds. The inquiry relates to activity or status during the calendar week, Sunday through Saturday, which includes the 12th of the month. This is known as the survey week. Actual field interviewing is conducted in the following week.

Inmates of institutions, members of the Armed Forces, and persons under 14 years of age are not covered in the regular monthly enumerations and are excluded from the population and labor force statistics shown in this report. Data on members of the Armed Forces, who are included as part of the categories "total noninstitutional population" and "total labor force," are obtained from the Department of Defense.

Each month, 47,000 occupied units are designated for interview. About 1,700 of these households are visited but interviews are not obtained because the occupants are not found at home after repeated calls or are unavailable for other reasons. This represents a noninterview rate for the survey of about 4 percent. In addition to the 47,000 occupied units, there are 7,500 sample units in an average month which are visited but found to be vacant or otherwise not to be enumerated. Part of the sample is changed each month. The rotation plan provides for three-fourths of the sample to be common from 1 month to the next, and one-half to be common with the same month a year ago.

CONCEPTS

Employed persons comprise (a) all those who during the survey week did any work at all as paid employees, in their own business, profession, or farm, or who worked 15 hours or more as unpaid workers in an enterprise operated by a member of the family, and (b) all those who were not working but who had jobs or businesses from which they were temporarily absent because of illness, bad weather, vacation, labor-management dispute, or personal reasons, whether or not they were paid by their employers for the time off, and whether or not they were seeking other jobs.

Each employed person is counted only once. Those who held more than one job are counted in the job at which they worked the greatest number of hours during the survey week.

Included in the total are employed citizens of foreign countries, temporarily in the United States, who are not living on the premises of an Embassy.

Excluded are persons whose only activity consisted of work around the house (such as own home housework, and painting or repairing own home) or volunteer work for religious, charitable, and similar organizations.

Unemployed persons comprise all persons who did not work during the survey week, who made specific efforts to find a job within the past 4 weeks, and who were available for work during the survey week (except for temporary illness). Also included as unemployed are those who did not work at all, were available for work, and (a) were waiting to be called back to a job from which they had been laid off; or (b) were waiting to report to a new wage or salary job within 30 days.

Duration of unemployment represents the length of time (through the current survey week) during which persons classified as unemployed had been continuously looking for work. For persons on layoff, duration of unemployment represents the number of full weeks since the termination of their most recent employment. A period of 2 weeks or more during which a person was employed or ceased looking for work is considered to break the continuity of the present period of seeking work. Average duration is an arithmetic mean computed from a distribution by single weeks of unemployment.

Unemployed persons by reasons for unemployment are divided into four major groups. (1) Job losers are persons whose employment ended involuntarily who immediately began looking for work and persons on layoff. (2) Job leavers are persons who quit or otherwise terminated their employment voluntarily and immediately began looking for work. (3) Reentrants are persons who previously worked at a full-time job lasting 2 weeks or longer but who were out of the labor force prior to beginning to look for work. (4) New entrants are persons who never worked at a full-time job lasting 2 weeks or longer.

Jobseekers are all unemployed persons who made specific efforts to find a job, sometime during the 4-week period preceding the survey week. Jobseekers do not include persons unemployed because they (a) were waiting to be called back to a job from which they had been laid off or (b) were waiting to report to a new wage or salary job within 30 days. Jobseekers are grouped by the methods used to seek work, including going to a public or private employment agency or to an employer directly, seeking assistance from friends or relatives, placing or answering ads, or utilizing some "other" method. Examples of the "other" category include being on a union or professional register, obtaining assistance from a community organization, or waiting at a designated pick-up point.

The civilian labor force comprises the total of all civilians classified as employed or unemployed in accordance with the criteria described above. The "total labor force" also includes members of the Armed Forces stationed either in the United States or abroad.

The unemployment rate represents the number unemployed as a percent of the civilian labor force. This measure can also be computed for groups within the labor force classified by sex, age, marital status, color, etc. The job-loser, job-leaver, reentrant, and new entrant rates are each calculated as a percent of the civilian labor force; the sum of the rates for the four groups thus equals the total unemployment rate.

Participation rates represent the proportion of the noninstitutional population that is in the labor force. Two types of participation rates are published: The total labor force participation rate, which is the ratio of the total labor force and the total noninstitutional population; and the civilian labor force participation rate, which is the ratio of the civilian labor force and the civilian noninstitutional population. Participation rates are usually published for sex-age groups, often cross-classified by other demographic characteristics such as color and educational attainment.

Not in labor force includes all civilians 16 years and over who are not classified as employed or unemployed. These persons are further classified as "engaged in own home housework," "in school," "unable to work" because of long-term physical or mental illness, and "other." The "other" group includes for the most part retired persons, those reported as too old to work, the voluntarily idle, and seasonal workers for whom the survey week fell in an "off" season and who were not reported as unemployed. Persons doing only incidental unpaid family work (less than 15 hours) are also classified as not in the labor force. For persons not in the labor force, data on previous work experience, intentions to seek work again, desire for a job at the time of interview, and reasons for not looking for work are compiled on a quarterly basis. As of January 1970, the detailed questions for persons not in the labor force are asked only in those households that are in the fourth and eighth months of the sample, i.e., the "outgoing" groups, those which had been in the sample for 3 previous months and would not be in for the subsequent month. Between 1967 and 1969, the detailed not-in-labor force questions were asked of persons in the first and fifth months in the sample, i.e., the "incoming" groups.

Occupation, industry, and class of worker for the employed apply to the job held in the survey week. Persons with two or more jobs are classified in the job at which they worked the greatest number of hours during the survey week. The unemployed are classified according to their latest full-time civilian job lasting 2 weeks or more. The occupation and industry groups used in data derived from the CPS household interviews are defined as in the 1970 Census of Population.

is available upon request.

The class-of-worker breakdown specifies "wage and salary workers," subdivided into private and government workers, "self-employed workers," and "unpaid family workers." Wage and salary workers receive wages, salary, commission, 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, or trade, or operate a farm. Unpaid family workers are persons working without pay for 15 hours a week or more on a farm or in a business operated by a member of the household to whom they are related by blood or marriage.

Hours of work statistics relate to the actual number of hours worked during the survey week. For example, a person who normally works 40 hours a week but who was off on the Columbus Day holiday would be reported as working 32 hours even though he was paid for the holiday.

For persons working in more than one job, the figures relate to the number of hours worked in all jobs during the week. However, all the hours are credited to the major job.

The distribution of employment by hours worked relate to persons "at work" during the survey week. At-work data differ from data on total employment because the latter include persons in zero-hours worked category, "with a job but not at work." Included in this latter group are persons who were on vacation, ill, involved in a labor dispute, or otherwise absent from their jobs for voluntary, noneconomic reasons.

Persons who worked 35 hours or more in the survey week are designated as working "full time;" persons who worked between 1 and 34 hours are designated as working "part time." Part-time workers are classified by their usual status at their present job (either full time or part time) and by their reason for working part time during the survey week (economic or other reasons). "Economic reasons" include: Slack work, material shortages, repairs to plant or equipment, start or termination of job during the week, and inability to find full-time work. "Other reasons" include: Labor dispute, bad weather, own illness, vacation, demands of home housework, school, no desire for full-time work, and full-time worker only during peak season. Persons on full-time schedules include, in addition to those working 35 hours Or more, those who worked from 1-34 hours for noneconomic reasons and usually work full time.

Full- and part-time labor force. The full-time labor force consists of persons working on full-time schedules, persons involuntarily working part time (part time for economic reasons), and unemployed persons seeking full-time jobs. The part-time labor force consists of persons working part time voluntarily and unemployed persons seeking part-time work. Persons with a job but not at work during the survey week are classified according to whether they usually work full or part time.

Labor force time lost is a measure of man-hours lost to the economy through unemployment and involuntary part-time employment and is expressed as a percent of potentially available man-hours. It is computed by assuming: (1) That unemployed persons looking for full-time work lost an average of 37.5 hours, (2) that those looking for part-time work lost the average number of hours actually worked by voluntary part-time workers during the survey week, and (3) that persons on part time for economic reasons lost the difference between 37.5 hours and the actual number of hours they worked.

White and Negro and other races are terms used to describe the color or race of workers. The Negro and other races

includes all persons who are observed in the enumeration process to be other than white. At the time of the 1970 Census of Population, 89 percent of the Negro and other races population group were Negro; the remainder were American Indians, Eskimos, Orientals, and other nonwhite. Tables in this volume which contain these data utilize the word "color" to so indicate. The term "Negro" is used in tables when the relevant data are provided for Negroes exclusively.

Spanish origin refers to persons who identified themselves in the enumeration process as Mexican, Puerto Rican living on the mainland, Cuban, Central or South American or other Spanish origin or descent. According to the 1970 Census, approximately 98 percent of their population is white.

Major activity: going to school and major activity: other are terms used to describe whether the activity of young persons during the reference week was primarily one of going to school or not. Statistics on major activities are published every month in table A-5 for 16-21 year-olds by employment status, color, sex, and, if unemployed, whether seeking full- or part-time work.

Household head. One person in each household is designated as the head. The head is usually the person regarded as the head by the members of the group. If a husband and wife family occupy the unit, the husband is designated as the head. The number of heads, therefore, is equal to the number of households.

Vietnam-era veterans are those who served in the Armed Forces of the United States after August 4, 1964. Tables for veterans in this volume are limited to men in the civilian noninstitutional population; i.e., veterans in institutions and females are excluded.

Nonveterans are males who never served in the Armed

Forces.

HISTORIC COMPARABILITY

Raised lower age limit

Beginning with data for 1967, the lower age limit for official statistics on persons in the labor force was raised from 14 to 16 years. At the same time, several definitions were sharpened to clear up ambiguities. The principal definitional changes were: (1) Counting as unemployed only persons who were currently available for work and who had engaged in some specific jobseeking activity within the past 4 weeks; an exception to the latter condition is made for persons waiting to start a new job in 30 days or waiting to be recalled from layoff; in the past, the current availability test was not applied and the time period for jobseeking was ambiguous; (2) counting as employed persons who were absent from their jobs in the survey week because of strikes, bad weather, etc. and those who were looking for other jobs; previously, these persons had been classified as unemployed; (3) sharpening the questions on hours of work, duration of unemployment, and self-employment in order to increase their reliability.

These changes did not affect the unemployment rate by more than one-fifth of a percentage point in either direction, although the distribution of unemployment by sex was affected. The number of employed was reduced about 1 million because of the exclusion of 14- and 15-year-olds. For persons 16 years and over, the only employment series appreciably affected were those relating to hours of work and class of worker. A detailed discussion of the changes and their effect on the various series is

contained in "New Definitions of Employment and Unemploy ment" by Robert L. Stein in the February 1967 issue of Employment and Earnings and Monthly Report on the Labor Force. Reprints may be obtained upon request.

Noncomparability of labor force levels

Before the changes introduced in 1967, the labor force data were not comparable for three earlier periods: (1) Beginning 1953, as a result of the introduction of data from the 1950 census into the estimation procedure, population levels were raised by about 600,000; labor force, total employment, and agricultural employment by about 350,000, primarily affecting the figures for totals and males; other categories were relative unaffected; (2) beginning 1960, the inclusion of Alaska and Hawaii resulted in an increase of about 500,000 in the population and about 300,000 in the labor force, four-fifths of this in nonagricultural employment; other labor force categories were not appreciably affected; (3) beginning 1962, the introduction of figures from the 1960 census reduced the population by about 50,000, labor force and employment by about 200,000; unemployment totals were virtually unchanged. In addition, beginning 1972, information from the 1970 census was introduced into the estimation procedures, producing an increase in the civilian noninstitutional population of about 800,000; labor force and employment totals were raised by a little more than 300,000, and unemployment levels and rates were essentially unchanged. A subsequent population adjustment based on the 1970 census was introduced in March 1973. This adjustment affected the white and Negro and other races groups but had little effect on totals. The adjustment resulted in the reduction of nearly 300,000 in the white population and an increase of the same magnitude in the Negro and other races population. Civilian labor force and total employment figures were affected to a lesser degree; the white labor force was reduced by 150,000, and the Negro and other races labor force rose by about 210,000. Unemployment levels and rates were not affected significantly.

Beginning in January 1974, the methodology used to prepare independent estimates of the civilian noninstitutional population was modified to an "inflation-deflation" approach. This change in the derivation of the population estimates had its greatest impact on estimates of 20-24 year-old malesparticularly those of Negro and other races-but had little effect on 16 and over totals. Additional information on the adjustment procedure appears in "CPS Population Controls Derived from Inflation-Deflation Method of Estimation" in the February 1974 issue of Employment and Earnings.

Changes in occupational classification system

Beginning with 1971, the comparability of occupational employment data was affected as a result of changes in census Occupational classifications introduced into the Current Population Survey (CPS). These changes stemmed from an exhaustive review of the classification system to be used for the 1970 Census of Population. This review, the most comprehensive since the 1940 census, was to reduce the size of large groups, to be more specific about general and "not elsewhere classified" groups, and to provide information on emerging significant Occupations. Differences in March 1970 employment levels tabulated on both the 1960 and 1970 classification systems ranged from a drop of 650,000 in operatives to an increase of

570,000 in service workers, much of which resulted from a shift between these two groups; the nonfarm laborers group increased by 420,000, and changes in other groups amounted to 220,000 or less.

An additional major group was created by splitting the operatives category into two: operatives, except transport, and transport equipment operatives. Separate data for these two groups first became available in January 1972. At the same time, several changes in titles, as well as in order of presentation, were introduced; for example, the title of the managers, officials, and proprietors group was changed to "managers and administrators, except farm," since only proprietors performing managerial duties are included in the category.

Apart from the effects of revisions in the occupational classification system beginning in 1971, comparability of occupational employment data was further affected in December 1971, when a question eliciting information on major activities or duties was added to the monthly CPS questionnaire in order to determine more precisely the occupational classification of individuals. This change resulted in several dramatic occupational shifts, particularly from managers and administrators to other groups. Thus, meaningful comparisons of occupational levels cannot be made between 1972 and earlier periods. However, revisions in the occupational classification system as well as in the CPS questionnaire are believed to have had but a negligible impact on unemployment rates.

Additional information on changes in the occupational classification system of the CPS appears in "Revisions in Occupational Classifications for 1971" and "Revisions in the Current Population Survey" in the February 1971 and February 1972 issues, respectively, of Employment and Earnings.

ESTIMATING METHODS

Under the estimation methods used in the CPS, all of the results for a given month become available simultaneously and are based on returns from the entire panel of respondents. There are no subsequent adjustments to independent benchmark data on labor force, employment, or unemployment. Therefore, revisions of the historical data are not an inherent feature of this statistical program.

1. Noninterview adjustment. The weights for all interviewed households are adjusted to the extent needed to account for occupied sample households for which no information was obtained because of absence, impassable roads, refusals, or unavailability of the respondent for other reasons. This adjustment is made separately by combinations of sample areas and, within these, for six groups-two race categories (white, and Negro and other races) within three residence categories. For sample areas which are standard metropolitan statistical areas (SMSA's), these residence categories are the central cities, and the urban and the rural balance of the SMSA's. For other sample areas, the residence categories are urban, rural nonfarm, and rural farm. The proportion of sample households not interviewed varies from 3 to 5 percent depending on weather, vacations, etc.

2. Ratio estimates. The distribution of the population selected for the sample may differ somewhat, by chance, from that of the Nation as a whole, in such characteristics as age, color, sex, and residence. Since these population characteristics are closely correlated with labor force participation and other principal measurements made from the sample, the latter estimates can be

known distribution of these population characteristics. This is accomplished through two stages of ratio estimates as follows:

a. First-stage ratio estimate. This is a procedure in which the sample proportions are weighted by the known 1970 Census data on the color-residence distribution of the population. This step takes into account the differences existing at the time of the 1970 Census between the color-residence distribution for the Nation and for the sample areas.

b. Second-stage ratio estimate. In this step, the sample proportions are applied to independent current estimates of the population by age, sex, and color. Prior to January 1974 these estimates were prepared by carrying forward the most recent census data (1970) after taking account of subsequent aging of the population, births, deaths, and migration between the United States and other countries.

Beginning in 1974, the "inflation-deflation" method of deriving independent population controls was introduced into the CPS estimation procedures. In this procedure, the most recent census population adjusted to include estimated net census undercount by age, sex, and color (i.e., "inflated") is carried forward to each subsequent month and later age by adding births, subtracting deaths, and adding net migration. These postcensal population estimates are then "deflated" to census level to reflect the pattern of net undercount in the most recent census by age, sex, and color. The actual percent change over time in the population in any age group is preserved. 3. Composite estimate procedure. In deriving statistics for a given month, a composite estimating procedure is used which takes account of net changes from the previous month for continuing parts of the sample (75 percent) as well as the sample results for the current month. This procedure reduces the sampling variability of month-to-month changes especially and of the levels for most items also.

Rounding of estimates

The sums of individual items may not always equal the totals shown in the same tables because of independent rounding of totals and components to the nearest thousand. Differences, however, are insignificant.

employment Unemployment

Reliability of the estimates

Since the estimates are based on a sample, they may differ from the figures that would have been obtained if it were possible to take a complete census using the same schedules and procedures.

The standard error is a measure of sampling variability, that is, the variations that might occur by chance because only a sample of the population is surveyed. The chances are about 2 out of 3 that an estimate from the sample would differ from a complete census by less than the standard error. The chances are about 19 out of 20 that the difference would be less than twice the standard error.

Table A shows the average standard error for the major employment status categories, by sex, computed from data for past months. Estimates of change derived from the survey are