Technical Notes for 2002 OES Estimates
Scope of the survey
The Occupational Employment Statistics (OES) survey is a semiannual mail survey measuring occupational employment and wage rates for wage and salary workers in nonfarm establishments, by industry, in the United States. (Guam, Puerto Rico, and the Virgin Islands also are surveyed, but their data are not included in this release.) In 2002, the OES survey switched from industry coding based on the Standard Industrial Classification (SIC) system to that based on the North American Industry Classification System (NAICS). The nationwide response rate for the 2002 survey was 78 percent for establishments, covering 71 percent of employment.
In November 2002, the OES survey changed from an annual survey of 400,000 establishments to a semiannual survey of 200,000 establishments. The OES survey samples and contacts establishments in May and November of each year and, over 3 years, contacts approximately 1.2 million establishments. The full 3-year sample allows the production of estimates at fine levels of geographic, industrial, and occupational detail.
In order to maintain adequate geographic, industrial, and occupational coverage through the implementation of NAICS and semiannual sampling, the 2002 data were combined with the annual samples from 1999, 2000, and 2001 for a total sample size of approximately 1.4 million establishments. Estimates from the OES are based on data collected using the Standard Occupational Classification (SOC) system. A brief description of this classification system is provided below.
The Occupational Classification Standard for 2002
In 1999, the OES survey began using the Office of Management and Budget's (OMB) occupational classification system, the Standard Occupational Classification (SOC) system. The SOC system is the first OMB-required occupational classification system for federal agencies. The OES survey categorizes workers in 1 of about 770 detailed occupations. Together, these detailed occupations comprise 22 major occupational groups. The major groups are as follows:
For more information about the SOC, please see the Bureau of Labor Statistics (BLS) Web site at https://www.bls.gov/soc.
The industry coding system for 2002
In 2002 the OES survey switched from using the Standard Industrial Classification (SIC) System to using the North American Industry Classification System (NAICS). Due to differences in NAICS and SIC structures, OES industry data for 2002 are not comparable with the SIC-based data for earlier years. For more information about NAICS, see the BLS Web site at https://www.bls.gov/bls/naics.htm. An establishment is defined as an economic unit that processes goods or provides services, such as a factory, mine, or store. The establishment is generally at a single physical location and is engaged primarily in one type of economic activity.
The OES survey covers all full- and part-time wage and salary workers in nonfarm industries. The survey does not include the self employed owners and partners in unincorporated firms, household workers, or unpaid family workers.
The OES survey includes establishments in NAICS sectors 11 (logging and agricultural support activities only), 21, 22, 23, 31-33, 42, 44-45, 48-49, 51, 52, 53, 54, 55, 56, 61, 62, 71, 72, 81 (except private households), state government, and local government. Data for the U.S. Postal Service and the federal government are universe counts obtained from the Postal Service and the Office of Personnel Management, respectively.
BLS funds the survey and provides the procedures and technical support, while the State Employment Security Agencies (SESAs) collect the data. BLS produces cross-industry NAICS estimates for the nation, states, and metropolitan statistical areas (MSAs). NAICS estimates are produced primarily at the 4-digit level with some 5-digit exceptions. BLS releases all cross-industry and national estimates, and the SESAs release industry estimates at the state and MSA levels.
The OES survey defines employment as the number of workers who can be classified as full-time or part-time employees, including workers on paid vacations or other types of leave; workers on unpaid short-term absences; salaried officers, executives, and staff members of incorporated firms; employees temporarily assigned to other units; and employees for whom the reporting unit is their permanent duty station regardless of whether that unit prepares their paycheck.
State Unemployment Insurance (UI) files provide the universe from which the OES survey draws its sample. The employment benchmarks are obtained from reports submitted by employers to the UI program. In some non-manufacturing industries, supplemental sources are used for establishments not reporting to the UI program. The OES survey sample is stratified by area, industry, and size class. Size classes are defined as follows:
UI reporting units with 250 or more employees are sampled with virtual certainty across a 3-year period. Generally, one-sixth of the certainty units are sampled in each panel in each state.
Occupational Employmentis the estimate of total wage and salary employment in an occupation across the industries in which that occupation was reported. The OES survey form sent to an establishment contains between 50 and 225 SOC occupations selected on the basis of the sampled establishment's industry classification and size class. To reduce paperwork and respondent burden, no survey form contains every SOC occupation. Thus, data for specific occupations are collected primarily from establishments in industries that are the predominant employers of workers in those occupations. Each survey form is structured, however, to allow a respondent to provide detailed occupational information for each worker at the establishment; that is, workers in unlisted occupations can have their occupations added to the survey form.
Wagesfor the OES survey are straight-time, gross pay, exclusive of premium pay. Base rate, cost-of-living allowances, guaranteed pay, hazardous-duty pay, incentive pay including commissions and production bonuses, tips, and on-call pay are included. Excluded are back pay, jury duty pay, overtime pay, severance pay, shift differentials, non-production bonuses, employer cost for supplementary benefits, and tuition reimbursements.
The OES survey collects wage data in 12 intervals. Employers report the number of employees in an occupation for each wage range. The wage intervals used for the 2002 survey are as follows:
A Mean (average) wagevalue is calculated for each wage interval based on occupational wage data collected by the BLS Office of Compensation and Working Conditions for the National Compensation Survey (NCS). These interval mean wage values are then attributed to all workers reported in the interval. To calculate the mean wage of each occupation, total weighted wages are summed across all intervals and divided by the occupation's weighted survey employment.
The mean wage value for the highest wage interval, $70.00 and over, is calculated after excluding data for pilots. Pilots comprise a large portion of the employment from the NCS survey that falls into the highest interval, and about one percent of the workers reported for the OES survey makes $70.00 and over. Since pilots work much fewer hours than workers in other occupations, their hourly wage rates are much higher than other occupations. After excluding pilots from the calculation, the mean wage for the highest interval was computed separately for 1999, 2000, 2001, and 2002. Then the average of these four mean wages was derived and used for all of the $70.00 and over data in the 2002 survey. The wages for this interval do not go through any wage updating procedures.
Annual wage. Many employees are paid at an hourly rate by their employers and may work more than or less than 40 hours per week. The annual wage estimates in this release are calculated by multiplying the mean hourly wage by a "year-round, full-time" figure of 2,080 hours (52 weeks by 40 hours). Thus, the annual wage estimates may not represent the actual annual pay received by the employee if they work more or less than 2,080 hours per year. Alternatively, some workers are paid based on an annual amount, but they generally do not work the usual 2,080 hours per year. Since the OES survey does not collect the actual number of hours worked, the hourly rate cannot be calculated with a reasonable degree of confidence from the annual wages. For this reason, the annual salary is directly calculated from reported survey data, and only annual wages are estimated for these occupations. Occupations that typically have a work year of less than 2,080 hours include musical and entertainment occupations, pilots and flight attendants, and teachers.
Hourly versus annual wage reporting. For each occupation, respondents are asked to report the number of employees paid within specific wage intervals. The intervals are defined both as hourly rates and the corresponding annual rates, where the annual rate for an occupation is calculated by multiplying the hourly wage rate by a typical work year of 2,080 hours. The responding establishment can reference either the hourly or the annual rate, but they are instructed to report the hourly rate for part-time workers.
Beginning in the fourth quarter of 2002, the OES survey samples approximately 200,000 establishments semiannually in the second and fourth quarters of the year, for a combined sample of 1.2 million different establishments over six semiannual panels. Until 2002, the survey sampled approximately 400,000 establishments in the fourth quarter of each year, for a 3-year combined sample size of 1.2 million. While estimates can be made from a single year or 2 years of data, the OES survey has been designed to produce estimates at a desired level of precision using the full 3 years of data. The 3-year sample allows the production of estimates at fine levels of geographical, industrial, and occupational detail. Since the 2002 sample was the first time that 200,000 establishments were sampled, the data were combined with annual survey data from 1999, 2000, and 2001, for a combined sample of approximately 1.4 million to provide adequate coverage of the sampling frame for these detailed estimates.
Producing estimates using the 3 years of sample data provides significant sampling error reductions (particularly for small geographic areas and occupations); however, it also has some quality limitations in that it requires the adjustment of earlier years' data to the current reference period, a procedure referred to as "wage updating."
Wage Updating. As noted above, combining multiple years of data has both statistical advantages and limitations. Significant reductions in sampling error can be achieved by taking advantage of 3 years of data, which covers over 70 percent of the employment in the United States. This feature is particularly important in improving the reliability of estimates for small domains in the population (that is, wage and employment estimates for detailed occupations in small areas). Combining multiple years of data also has been necessary to obtain full coverage of establishments with 250 or more workers that are sampled with certainty.
Starting with the 1997 estimates, the OES program has used the over-the-year fourth-quarter wage changes from the BLS Employment Cost Index (ECI) to adjust prior year survey data before combining it with the current year's data. The wage updating procedure assumes that each occupation's wage, as measured in the earlier years, moves according to the average movement of its occupational division and that there are no major geographic or detailed occupational differences.
2002 OES survey estimates. The 2002 OES survey estimates are based on data collected from establishments for the 1999, 2000, 2001, and 2002 samples. The 2002 estimates use the wage-updating methodology introduced in 1997. In addition, the 2002 estimates use the estimation methodology introduced in 1997, which uses a "nearest neighbor" imputation approach for nonresponse and applies employment benchmarks at the state-MSA/4-digit NAICS (with 5- digit exceptions) /size class level.
Reliability of the estimates. Statistics based on establishment surveys are subject to both sampling and nonsampling error. When a sample of the population is surveyed, there is a chance that the sample estimate of a characteristic may differ from the population value of that characteristic. The difference between the sample estimate and the population value will vary depending on the particular sample selected. This variability is measured by the sampling error (SE). If the sampling and estimation process using the same survey design was repeated, 90 percent of the intervals created by adding and subtracting 1.645 standard errors from the sample estimate would include the population value. This interval is called a 90-percent confidence interval.
The OES survey produces estimates of the relative standard error (RSE). The RSE is defined as the SE divided by the estimated value as computed from the sample. This statistic provides a measure of the relative precision of the sample estimates. The SE may be obtained by multiplying the RSE by the sample estimate. RSE estimates are produced for both occupational employment and mean wage estimates. The employment RSE values are estimated using a subsample replication technique known as the Jackknife (random group) variance estimation method. The mean wage RSE values are estimated using a variance components model that accounts for both the observed and unobserved components of the wage data. The variances of the unobserved components of the wage data are calculated from the BLS National Compensation Survey. In general, estimates involving many establishments have lower relative standard errors than estimates involving few establishments. If the distributional assumptions of the models are violated, the resulting confidence interval may not reflect the prescribed level of confidence.
The 2002 OES national data by occupation, comparable to data in table 1, will be available soon on the Internet (https://www.bls.gov/oes). Users also may access each occupation's definition and percentile wages. The 2002 cross-industry data for states and metropolitan areas will be available on the BLS Web site in late November. Industry staffing patterns at the 4- and 5-digit NAICS levels also will be available from the Internet beginning in late November. These data will include industry-specific occupational employment and wage data.
For additional information, contact the Office of Employment and Unemployment Statistics, Division of Occupational Employment Statistics, Room 2135, 2 Massachusetts Avenue, NE, Washington, DC, 20212; telephone: 202-691-6569; e-mail: OES staff.
Information in this release will be made available to sensory impaired individuals upon request. Voice phone: 202-691-5200; TDD message referral phone number: 1-800-877-8339.
Last Modified Date: April 9, 2018