Technical Note Scope of the survey The Occupational Employment and Wage Statistics (OEWS) survey is a semiannual survey measuring occupational employment and wage rates for wage and salary workers in nonfarm establishments in the United States. The OEWS 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 OEWS 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. OEWS estimates are constructed from a sample of about 1.1 million establishments. Each year, two semiannual panels of approximately 180,000 to 185,000 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 2020 estimates are based on responses from six semiannual panels collected over a 3-year period: May 2020, November 2019, May 2019, November 2018, May 2018, and November 2017. The unweighted sampled employment of 83 million across all six semiannual panels represents approximately 56 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 69 percent based on establishments and 66 percent based on weighted sampled employment. The occupational coding system The May 2020 OEWS estimates contain nearly 800 occupational categories based on the Office of Management and Budget's 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 2020 OEWS estimates use a hybrid of the 2010 and 2018 SOC systems. For more information on the hybrid classification system, please see the "Changes and special procedures in the May 2020 estimates" section of this technical note. The industry coding system The May 2020 OEWS 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 OEWS 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. OEWS 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 OEWS 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 OEWS 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 OEWS 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 OEWS 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. OEWS receives wage rate data for the federal government, the U.S. Postal Service, and most state governments. For the remaining establishments, the OEWS 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 OEWS survey is designed to produce estimates by combining six panels of data collected over a 3-year period. Each OEWS panel contains approximately 180,000 to 185,000 establishments. 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 panel's reference period. The OEWS program uses the BLS Employment Cost Index (ECI) to adjust survey data from prior panels before combining them with the current panel's data. The wage updating procedure adjusts each detailed occupation's 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 2019 and May 2020 employment) from the BLS Quarterly Census of Employment and Wages (QCEW) to employment totals from the OEWS survey. Changes and special procedures in the May 2020 estimates Due to features of the OEWS methodology, the May 2020 estimates do not fully reflect the impact of the COVID-19 pandemic. Because 5 of the 6 survey panels used to produce the estimates date from before the COVID-19 pandemic, only the most recent (May 2020) survey panel will reflect changes in occupational proportions related to the pandemic. In addition, because the OEWS employment estimates are benchmarked to the average of QCEW employment for November 2019 and May 2020, the estimates will reflect only part of the pandemic's impact on employment as of May 2020. Although the May 2020 QCEW data reflect the early employment effects of the COVID-19 pandemic, the November 2019 QCEW employment data precede the COVID-19 pandemic, and therefore do not reflect its impact. As a result of the pandemic, response rates for the November 2019 and May 2020 panels were lower in some areas. Lower response rates may negatively affect data availability and data quality. For more information about the impact of the COVID-19 pandemic on OEWS, see www.bls.gov/covid19/effects-of-covid-19-pandemic-on-occupational-employment-and-wage-statistics.htm. With the May 2019 estimates, the OEWS program began implementing the 2018 Standard Occupational Classification (SOC) system. Because the May 2020 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, OEWS will not publish data for some 2018 SOC minor groups and broad occupations in the May 2020 estimates. The May 2021 estimates, to be published in Spring 2022, will be the first OEWS estimates based entirely on survey data collected using the 2018 SOC. In addition, the OEWS program has replaced some 2018 SOC detailed occupations with SOC broad occupations or OEWS-specific aggregations. These include home health aides and personal care aides, for which OEWS 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 2020 OEWS estimates is available at www.bls.gov/oes/soc_2018.htm and in the OEWS frequently asked questions at www.bls.gov/oes/oes_ques.htm#qf10. The May 2020 OEWS estimates use the metropolitan area definitions delineated in Office of Management and Budget (OMB) Bulletin 17-01. For more information, please see www.bls.gov/oes/current/msa_def.htm. For more information Answers to frequently asked questions about the OEWS data are available at www.bls.gov/oes/oes_ques.htm.