Technical Note Scope of the survey The Occupational Employment Statistics (OES) survey is a semiannual survey measuring occupational employment and wage rates for wage and salary workers in nonfarm establishments in the United States. The OES data available from BLS include cross- industry occupational employment and wage estimates for the nation; over 580 areas, including states and the District of Columbia, metropolitan statistical areas (MSAs), nonmetropolitan areas, and territories; national industry-specific estimates at the NAICS sector, 3-digit, most 4-digit, and selected 5- and 6-digit industry levels; and national estimates by ownership across all industries and for schools and hospitals. The OES survey is a cooperative effort between BLS and the State Workforce Agencies (SWAs). BLS funds the survey and provides the procedures and technical support, while the State Workforce Agencies collect most of the data. OES estimates are constructed from a sample of about 1.1 million establishments. Each year, two semiannual panels of approximately 180,000 to 200,000 sampled establishments are contacted, one panel in May and the other in November. Responses are obtained by mail, Internet or other electronic means, email, telephone, or personal visit. The May 2019 estimates are based on responses from six semiannual panels collected over a 3-year period: May 2019, November 2018, May 2018, November 2017, May 2017, and November 2016. The unweighted sampled employment of 83 million across all six semiannual panels represents approximately 57 percent of total national employment. The overall national response rate for the six panels, based on the 50 states and the District of Columbia, is 71 percent based on establishments and 68 percent based on weighted sampled employment. The occupational coding system The May 2019 OES estimates contain nearly 800 occupational categories based on the Office of Management and Budgetís Standard Occupational Classification (SOC) system. Together, these occupations make up 22 of the 23 SOC major occupational groups. Major group 55, Military Specific Occupations, is not included. For more information about the SOC system, please see the BLS website at www.bls.gov/soc/. The May 2019 OES estimates are the first set of OES estimates to be based in part on survey data collected using the 2018 SOC. These estimates use a hybrid of the 2010 and 2018 SOC systems. For more information on the hybrid classification system used in the May 2019 OES estimates, please see the "Changes to the May 2019 estimates" section of this technical note. The industry coding system The May 2019 OES estimates use the 2017 North American Industry Classification System (NAICS). For more information about NAICS, see the BLS website at www.bls.gov/bls/naics.htm. The OES survey excludes the majority of the agricultural sector, with the exception of logging (NAICS 113310), support activities for crop production (NAICS 1151), and support activities for animal production (NAICS 1152). Private households (NAICS 814) also are excluded. OES federal government data include the U.S. Postal Service and the federal executive branch only. All other industries, including state and local government, are covered by the survey. Survey sample The OES survey draws its sample from state unemployment insurance (UI) files. Supplemental sources are used for rail transportation (NAICS 4821) and Guam because they do not report to the UI program. The OES survey sample is stratified by metropolitan and nonmetropolitan area, industry, and size. To provide the most occupational coverage, larger employers are more likely to be selected than smaller employers. A census is taken of the executive branch of the federal government, the U.S. Postal Service, and state government. Concepts Occupational employment is the estimate of total wage and salary employment in an occupation. The OES survey defines employment as the number of workers who can be classified as full- or part-time employees, including workers on paid vacations or other types of paid 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. The survey does not include the self-employed, owners and partners in unincorporated firms, household workers, or unpaid family workers. Wages for 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; and tips are included. Excluded are overtime pay, severance pay, shift differentials, nonproduction bonuses, employer cost for supplementary benefits, and tuition reimbursements. OES receives wage rate data for the federal government, the U.S. Postal Service, and most state governments. For the remaining establishments, the OES survey data are placed into 12 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 establishments are instructed to report the hourly rate for part-time workers, and to report annual rates for occupations that are typically paid at an annual rate but do not work 2,080 hours per year, such as teachers, pilots, and flight attendants. Other workers, such as some entertainment workers, are paid hourly rates, but generally do not work 40 hours per week, year round. For these workers, only an hourly wage is reported. Estimation methodology The OES survey is designed to produce estimates by combining six panels of data collected over a 3-year period. Each OES panel contains approximately 180,000 to 200,000 establishments. Recent OES survey panels have a reduced sample; see the "Changes to the May 2019 estimates" section below for more information. The full six-panel sample of 1.1 million establishments allows the production of estimates at detailed levels of geography, industry, and occupation. Wage updating. Significant reductions in sampling errors are obtained by combining six panels of data, particularly for small geographic areas and occupations. Wages for the current panel need no adjustment. However, wages in the five previous panels need to be updated to the current panelís reference period. The OES program uses the BLS Employment Cost Index (ECI) to adjust survey data from prior panels before combining them with the current panelís data. The wage updating procedure adjusts each detailed occupationís wage rate, as measured in the earlier panel, according to the average movement of its broader occupational division. Imputation. Some establishments do not respond for a given panel. For most employers, a "nearest neighbor" hot deck imputation procedure is used to impute missing occupational employment totals. A variant of mean imputation is used to impute missing wage distributions. In some cases, data for nonrespondents are available from earlier panels. In those cases, the older data may be used and aged to represent the current reference period. Weighting and benchmarking. The sampled establishments are weighted to represent all establishments for the reference period. Weights are further adjusted by the ratio of employment totals (the average of November 2018 and May 2019 employment) from the BLS Quarterly Census of Employment and Wages to employment totals from the OES survey. Changes to the May 2019 estimates With the May 2019 estimates, the OES program has begun implementing the 2018 Standard Occupational Classification (SOC) system. Each set of OES estimates is calculated from six panels of survey data collected over three years. Because the May 2019 estimates are based on a combination of survey data collected using the 2010 SOC and survey data collected using the 2018 SOC, these estimates use a hybrid of the two classification systems that contains some combinations of occupations that are not found in either the 2010 or 2018 SOC. These combinations may include occupations from more than one 2018 SOC minor group or broad occupation. Therefore, OES will not publish data for some 2018 SOC minor groups and broad occupations in the May 2019 estimates. The May 2021 estimates, to be published in Spring 2022, will be the first OES estimates based entirely on survey data collected using the 2018 SOC. In addition, the OES program has replaced some 2018 SOC detailed occupations with SOC broad occupations or OES-specific aggregations. These include home health aides and personal care aides, for which OES will publish only the 2018 SOC broad occupation 31-1120 Home Health and Personal Care Aides. More information on the occupational classification system used in the May 2019 OES estimates is available at www.bls.gov/oes/soc_2018.htm and in the OES frequently asked questions at www.bls.gov/oes/oes_ques.htm#qf10. The May 2019 OES estimates use the metropolitan area definitions delineated in Office of Management and Budget (OMB) Bulletin 17-01, which add a new Metropolitan Statistical Area (MSA) for Twin Falls, Idaho. For more information on the area definitions used in the May 2019 estimates, please see www.bls.gov/oes/current/msa_def.htm. The OES sample has been reduced in recent survey panels. The May 2019 OES survey panel had a sample of approximately 183,000 establishments. The November 2017, May 2018, and November 2018 survey panels each had a sample of approximately 186,000 establishments. The May 2017 panel sample consisted of approximately 195,000 establishments, and the November 2016 panel sample consisted of approximately 202,000 establishments. For more information Answers to frequently asked questions about the OES data are available at www.bls.gov/oes/oes_ques.htm.