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The OES program in its current form dates to 1996 and began publishing occupational employment and wage estimates in 1997. Since 1997, the OES data have undergone a number of changes, including changes to the occupational and industry classification systems used, changes to the metropolitan and nonmetropolitan area definitions, and changes to the sample size and survey reference dates.
Changes in occupational classification
The 1997 and 1998 OES estimates used an occupational classification system that was specific to the OES program. In 1999, the OES program adopted the federal Standard Occupational Classification (SOC) system. The 1999–May 2009 estimates are based on the 2000 version of the SOC.
Between May 2010 and May 2012, the OES program transitioned to the 2010 SOC. Because each set of OES estimates is produced by combining three years of survey data, the May 2010 and May 2011 estimates were based on a combination of newer survey panels collected using the 2010 SOC and older survey panels collected using the 2000 SOC. Therefore, these estimates used a hybrid of the 2000 and 2010 systems that included some OES-specific combinations of occupations. The May 2012 estimates were the first set of estimates based fully on the 2010 SOC. More information about the hybrid system used in the May 2010 and May 2011 estimates is available in the OES frequently asked questions.
Beginning with the May 2017 estimates, the OES program replaced 21 SOC detailed occupations with SOC broad occupations or OES-specific combinations of detailed occupations. These changes were made to improve data quality in cases where occupations are similar and it is difficult to obtain the information needed to code accurately to the detailed occupational level. More information about these aggregations is available at www.bls.gov/oes/changes_2017.htm.
The OES program began implementing the 2018 SOC with the May 2019 estimates. Because of the OES 3-year methodology, the May 2019 and May 2020 estimates will use a hybrid of the 2010 and 2018 SOCs that includes some combinations of occupations that are not found in either version of the system. The May 2021 estimates will be the first estimates based entirely on survey data collected using the 2018 SOC. More information on the hybrid classification system used in the May 2019 estimates is available on the OES 2018 SOC implementation page and in the frequently asked questions.
The May 2019 estimates also introduced some new occupational aggregations designed to improve data quality, along with changes to some of the occupational aggregations introduced in May 2017.
Changes in industry classification and survey scope
The 1997–2001 OES estimates used the Standard Industrial Classification (SIC) system. In 2002, the OES program switched from the SIC to the 2002 North American Industry Classification System (NAICS). Updates to the NAICS system were adopted in the May 2008 estimates (2007 NAICS), May 2012 estimates (2012 NAICS), and May 2017 estimates (2017 NAICS).
Beginning with the May 2014 estimates, gambling establishments and casino hotels owned by local governments were moved from the OES local government industry (9993) to NAICS 7132 Gambling Industries and 72112 Casino Hotels, respectively.
The May 2017 estimates included for the first time some establishments that were reclassified from NAICS 814 Private Households, which is out of scope for the OES survey, to NAICS 624120 Services for the Elderly and Persons with Disabilities, which is in scope. As a result, the May 2017 estimates may show increased employment in occupations that are common in NAICS 624120.
Changes to area definitions
The OES program uses standard metropolitan area definitions from the U.S. Office of Management and Budget (OMB). For the New England states, OES uses the New England City and Town Area (NECTA) definitions rather than the Metropolitan Statistical Area (MSA) definitions. The OES nonmetropolitan areas use definitions that are specific to the OES program and are developed in cooperation with the state workforce agencies.
The OES program implemented major revisions to the area definitions in the May 2005 and May 2015 estimates. The May 2005 estimates introduced revised OMB area definitions based on the results of the 2000 decennial census. The May 2015 estimates introduced revised definitions based on the 2010 census. In addition to the major revisions in May 2005 and May 2015, smaller revisions were implemented in other years. Because the OES nonmetropolitan areas cover the remainder of each state outside of the OMB-defined metropolitan areas, changes to the metropolitan area definitions may also affect the nonmetropolitan area definitions.
With the May 2018 estimates, the OES program reduced the level of geographic detail available in some areas. For the 11 large metropolitan areas that are further broken down into metropolitan divisions, OES no longer publishes data for the divisions. Data for these 11 areas are now available at the Metropolitan Statistical Area (MSA) or New England City and Town Area (NECTA) level only. In addition, some smaller nonmetropolitan areas were combined to form larger nonmetropolitan areas. More information on these area changes is available at www.bls.gov/oes/areas_2018.htm.
Changes to sample size and reference period
Before 2002, the OES program collected data from 400,000 business establishments annually with a 4th quarter reference date. Survey respondents were asked to provide data as of an October, November, or December payroll, depending on the specific respondent.
In 2002, OES switched to semiannual data collection to reduce seasonal effects. Data were collected in two semiannual survey panels of approximately 200,000 business establishments each, with reference dates of May 12 and November 12.
The OES program also published estimates semiannually in 2003 and 2004. In 2005, the OES program returned to publishing data annually, but retained semiannual data collection.
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.
Data before 1997
Data from the immediate predecessor to the current OES program are available at the bottom of the main OES data page. These data cover the period 1988–1995 and are not directly comparable to more recent OES data. The 1988-1995 data consist only of national occupational employment estimates by 2- and 3-digit SIC industry, with data for each industry available only once every three years. These estimates do not contain wage data or state and area data. Because data are not available for all industries in a given year, it is not possible to calculate total national employment in an occupation from these estimates.