This section of the Review presents the principal statistical series collected and calculated by the Bureau of Labor Statistics. A brief introduction to each group of tables provides definitions, notes on the data, sources, and other material usually found in footnotes.

Readers who need additional information are invited to consult the BLS regional offices listed on the inside front cover of this issue of the Review. Some general notes applicable to several series are given below.

Seasonal adjustment. Certain monthly and quarterly data are adjusted to eliminate the effect of such factors as climatic conditions, industry production schedules, opening and closing of schools, holiday buying periods, and vacation practices, which might otherwise mask short-term movements of the statistical series. Tables containing these data are identified as "seasonally adjusted." Seasonal effects are estimated on the basis of past experience. When new seasonal factors are computed each year, revisions may affect seasonally adjusted data for several preceding years. For a technical discussion of the method used to make seasonal adjustments, see "Appendix A. The BLS Seasonal Factor Method," BLS Handbook of Methods for Surveys and Studies, Bulletin 1910 (Bureau of Labor Statistics, 1976), pp. 272-78, and X-11 Variant of the Census Method II Seasonal Adjustment Program, Technical Paper No. 15 (Bureau of the Census, 1967). Seasonally adjusted employment data in tables 2-7 were last revised in the February 1979 issue of the Review to reflect the preceding year's experience. Annual revision of the seasonally adjusted payroll data in tables 11, 13, 16, and 18 was last introduced in the November 1978 issue of the Review. New seasonal factors for productivity data in tables 33 and 34 are usually introduced in the September issue. Seasonally adjusted indexes and percent changes from month to month and from quarter to quarter are published for numerous Consumer and Producer Price Index series. However, seasonally adjusted indexes are not published for the U.S. average All Items CPI. Only seasonally adjusted percent changes are available for this series.

Adjustments for price changes. Some data are adjusted to eliminate the effect of changes in price. These adjustments are made by dividing current dollar values by the Consumer Price Index or the appropriate component of the index, then multiplying by 100. For example, given a current hourly wage rate of $3 and a current price index number of 150, where 1967 = 100, the hourly rate expressed in 1967 dollars is $2 ($3/150 X 100 $2). The resulting values are described as "real," "constant," or "1967" dollars.

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Availability of information. Data that supplement the tables in this section are published by the Bureau of Labor Statistics in a variety of sources. Press releases provide the latest statistical information published by the Bureau; the major recurring releases are published according to the schedule given below. The Handbook of Labor Statistics 1977, Bulletin 1966, provides more detailed data and greater historical coverage for most of the statistical series presented in the Monthly Labor Review. More information from the household and establishment surveys is provided in Employment and Earnings, a monthly publication of the Bureau, and in two comprehensive data books issued annually-Employment and Earnings, United States and Employment and Earnings, States and Areas. More detailed information on wages and other aspects of collective bargaining appears in the monthly periodical, Current Wage Developments. More detailed price information is published each month in the periodicals, the CPI Detailed Report and Producer Prices and Price Indexes. Selected key statistical series are presented graphically in the monthly Chartbook on Prices, Wages, and Productivity.

EMPLOYMENT DATA in this section are obtained from the Current Population Survey, a program of personal interviews conducted monthly by the Bureau of the Census for the Bureau of Labor Statistics. The sample consists of about 56,000 households, selected to represent the U.S. population 16 years of age and older. Households are interviewed on a rotating basis, so that three-fourths of the sample is the same for any 2 consecutive months.

Definitions

Employed persons are (1) those who worked for pay any time during the week which includes the 12th day of the month or who worked unpaid for 15 hours or more in a family-operated enterprise and (2) those who were temporarily absent from their regular jobs because of illness, vacation, industrial dispute, or similar reasons. A person working at more than one job is counted only in the job at which he or she worked the greatest number of hours.

Unemployed persons are those who did not work during the survey week, but were available for work except for temporary illness and had looked for jobs within the preceding 4 weeks. Persons who were available for work but did not work because they were on layoff or waiting to start new jobs within the next 30 days are also counted among the unemployed. The unemployment rate represents the number unemployed as a percent of the civilian labor force.

The civilian labor force consists of all employed or unemployed persons in the civilian noninstitutional population; the total labor force includes military personnel. Persons not in the labor force are those not classified as employed or unemployed; this group includes persons retired, those engaged in their own housework, those not

working while attending school, those unable to work because of longterm illness, those discouraged from seeking work because of personal or job market factors, and those who are voluntarily idle. The noninstitutional population comprises all persons 16 years of age and older who are not inmates of penal or mental institutions, sanitariums, or homes for the aged, infirm, or needy.

Full-time workers are those employed at least 35 hours a week; part-time workers are those who work fewer hours. Workers on parttime schedules for economic reasons (such as slack work, terminating or starting a job during the week, material shortages, or inability to find full-time work) are among those counted as being on full-time status, under the assumption that they would be working full time if conditions permitted. The survey classifies unemployed persons in full-time or part-time status by their reported preferences for full-time or part-time work.

Notes on the data

From time to time, and especially after a decennial census, adjustments are made in the Current Population Survey figures to correct for estimating errors during the preceding years. These adjustments affect the comparability of historical data presented in table 1.

Data for periods prior to January 1978 are not strictly comparable with current data because of the introduction of an expansion in the sample and revisions in the estimation procedures. For an explanation of the supplementation procedures and an indication of the differences, see "Revisions in the Current Population Survey in January 1978," Employment and Earnings, February 1978, pp. 7-10. Data in tables 2-7 are seasonally adjusted, based on the seasonal experience through December 1978.

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