Handbook of Methods Survey of Occupational Injuries and Illnesses Concepts

The Occupational Safety and Health Act of 1970 called for a wider statistical net to gather work injury and illness data and to measure their numbers and incidence rates. The current mandatory Survey of Occupational Injuries and Illnesses (SOII), modified on several occasions to incorporate various changes discussed in later sections, still meets the basic requirements of the 1970 act for counts and rates covering a broad spectrum of work injuries and illnesses in various work settings. In response to a 1987 National Academy of Sciences (NAS) study (described in more detail in the history section), SOII began to collect information on the circumstances of nonfatal cases involving days away from work and the characteristics of workers sustaining such injuries and illnesses for the 1992 calendar year. SOII is a federal/state program in which employers’ reports are collected and processed by state agencies in cooperation with the Bureau of Labor Statistics (BLS).

SOII estimates the number and frequency (incidence rates) of workplace injuries and illnesses based on recordkeeping logs kept by employers during the year. These records reflect not only the year’s injury and illness experience, but also the employer’s understanding of which cases are work-related under recordkeeping guidelines promulgated by the U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA). Although SOII uses OSHA’s recordkeeping guidelines to facilitate convenient collection of data, it is not administered by OSHA. In addition, the scope of SOII encompasses industries not regulated by OSHA, such as railroad and mining. Information collected through the program is used for purely statistical purposes, will not be viewed by OSHA, and cannot be used for any regulatory purpose.

Besides injury and illness counts, survey respondents also are asked to provide additional information for the subset of nonfatal cases that involved at least 1 day away from work, beyond the day of injury or onset of illness. Employers answer several questions about these cases, including the demographics of the worker, the nature of the disabling condition, the event and source producing that condition, and the part of body affected.

SOII definitions

The following definitions of nonfatal occupational injuries and illnesses used in SOII are the same as those established in the recordkeeping guidelines of OSHA, and used by employers to keep logs and case details of such incidents throughout the survey (calendar) year. (See more info section for citations of instructional materials useful in understanding the types of cases recorded under current recordkeeping guidelines.)

Recording criteria

Nonfatal recordable workplace injuries and illnesses are those that result in any one or more of the following:

• Loss of consciousness
• Days away from work
• Restricted work activity or job transfer
• Medical treatment beyond first aid

In addition to these four criteria, employers must also record any significant work-related injuries or illnesses that are diagnosed by a physician or other licensed healthcare professional or other instances that meet additional criteria discussed below. Significant work-related injuries or illnesses include cancers, chronic irreversible diseases, fractured or cracked bones (including teeth), or punctured eardrums. Additional cases that must be recorded as workplace injuries or illnesses include the following:

• Any needlestick injury or cut from a sharp object that is contaminated with another person’s blood or other potentially infectious material
• Any case requiring an employee to be medically removed under the requirements of an OSHA health standard
• Tuberculosis infection as evidenced by a positive skin test or diagnosis by a physician or other licensed health care professional after exposure to a known case of active tuberculosis
• An employee’s hearing test (audiogram) reveals 1) that the employee has experienced a standard threshold shift (STS) in hearing in one or both ears (averaged at 2kHz, 3kHz, and 4kHz) and 2) the employee’s total hearing level is 25 decibels (dB) or more above audiometric zero (also averaged at 2kHz, 3kHz, and 4kHz) in the same ear(s) as the STS.

Additional details regarding recordability of nonfatal work-related injuries and illnesses can be found in Detailed guidance for OSHA’s injury and illness recordkeeping rule.

Injuries and illnesses. The distinction between occupational injury and occupational illness was eliminated from OSHA recordkeeping guidelines when revisions were implemented in 2002. The OSHA guidelines now define an injury or illness as an abnormal condition or disorder. For purposes of clarification for SOII, these terms are still defined separately. Nature codes from the Occupational Injury and Illness Classification System (OIICS) manual are used to code distinct injury and illness cases.

• Occupational injury is any injury, such as a cut, fracture, sprain, amputation, and so forth, that results from a work-related event or from a single instantaneous exposure in the work environment.
• Occupational illness is any abnormal condition or disorder caused by exposure to factors associated with employment, other than those resulting from an instantaneous event or exposure. It includes acute and chronic illnesses or diseases that may be caused by inhalation, absorption, ingestion, or direct contact. Five categories of occupational illnesses and disorders are used to classify recordable illnesses, described as follows. Examples of each category are provided, but these are not a complete listing of the types of illnesses and disorders that are counted under each category. (See the OIICS manual for a more comprehensive list of injuries and illnesses and their associated codes.)

Case types. Nonfatal injury and illness estimates are tabulated from SOII data for several types of cases, including the following:

• Days away from work, job restriction, or transfer (DART) cases are those which involve days away from work beyond the day of injury or onset of illness, or days of job transfer or restricted work activity, or both.
• Days away from work (DAFW) cases are those which result in days away from work (beyond the day of injury or onset of illness). The number of days away from work for these cases is determined according to the number of calendar days (not workdays) that an employee was unable to work, even if the employee was not scheduled to work those days. The day on which the employee was injured or became ill is not counted. These cases may also include days of job transfer or restricted work activity in addition to days away from work. Take the case of an employee who suffers a work-related injury resulting in 5 days away from work. Upon returning to work, the employee was unable to perform normal duties associated with the job for an additional 3 days (i.e., the employee was on restricted work activity). This case would be recorded as a days-away-from-work case with 5 days away from work and 3 days of restricted work activity. The number of days away for which employers are required to report may be “capped” at 180 calendar days.
• Days of job transfer or restriction cases (DJTR) are those which result only in job transfer or restricted work activity. This occurs when, as the result of a work-related injury or illness, an employer keeps or healthcare professional recommends keeping an employee from doing the routine functions of his or her job or from working the full workday that the employee would have been scheduled to work before the injury or illness occurred. This may include the following instances:
  • An employee is assigned to another job temporarily.
  • An employee works at a permanent job less than full time.
  • An employee works at a permanently assigned job but is unable to perform all duties normally connected with it.
  • The day on which the injury or illness occurred is not counted as a day of job transfer or restriction. Workers who continue working after incurring an injury or illness in their regularly scheduled shift but produce fewer goods or services are not considered to be in restricted activity status. They must be restricted from performing their routine work functions to be counted in this category.
• Other recordable cases are those which are recordable injuries or illnesses under OSHA recordkeeping guidelines but do not result in any days away from work, nor a job transfer or restriction, beyond the day of the injury or onset of illness. For example, John cut his finger on machinery during his Wednesday afternoon work shift. The injury required medical attention, for which John received sutures at the local emergency room. John was able to return to his normally scheduled workday on the following day (Thursday) and performed his typical work duties without any restrictions.

Differences in coverage between SOII and CFOI

SOII covers private, state government, and local government wage and salary workers, while CFOI also covers workers on small farms, the self-employed, family workers, and federal government workers.

Because of these scope coverage differences, outlined in table 1, CFOI and SOII data are not directly comparable.

Injury, illness, and fatality common classifications

BLS publishes statistics on nonfatal workplace injuries and illnesses from SOII and fatal workplace injuries from CFOI. Most of these data can be located at the IIF homepage. SOII and CFOI share several systems to classify industry, occupation, case circumstances, and worker characteristics. Changes among these systems over the past several years have affected SOII (both estimates by industry and by case circumstances and worker characteristics) and CFOI outputs, as described below. More information on these classifications and how they have affected the data series in the online notice, the presentation section and the history section.

BLS has long relied on state, regional, and national staff to manually assign SOC and Occupational Injury and Illness Classification System (OIICS) codes, but in recent years their role in SOII coding has begun to shift. Motivated by a desire to improve coding quality and by evidence that new automated techniques might result in classification accuracies similar to those achieved by staff, BLS began using computers to automatically assign SOC codes to a portion of SOII cases starting with reference year 2014 data.^⁠1 For reference year 2015, BLS expanded autocoding further to include some OIICS coding as well. BLS state and regional staff remain responsible for assigning many codes and are instructed to review and validate all automatically assigned codes.

Occupational Injury and Illness Classification System (OIICS)

BLS developed OIICS to provide a consistent set of classifications of the circumstances of the characteristics associated with workplace injuries, illnesses, and fatalities. OIICS is used to classify the circumstances of each injury, illness, and fatality case. BLS developed the original OIICS structure with input from data users and states participating in the BLS Occupational Safety and Health Statistics (OSHS) federal/state cooperative programs. The original system was released in December 1992 and approved for use as the American National Standard for Information Management for Occupational Safety and Health in 1995 (ANSI Z16.2—1995). In September 2007, BLS updated OIICS classifications to incorporate various interpretations and corrections.

The OIICS revision in September 2010 was the first major revision since this classification system was first developed in 1992. BLS implemented a revised OIICS structure based on input from many stakeholders. In February 2008, BLS issued a Federal Register Notice requesting suggestions for proposed changes to OIICS. In addition, BLS sent out numerous letters and emails to stakeholders who use the OIICS to classify injury and illness data. In April 2010, BLS issued a draft of the revised OIICS 2.01 manual to interested parties requesting their comments. The team evaluated the comments received, made revisions, and issued the completed OIICS 2.01 manual in September 2010. Due to substantial differences between OIICS 2.01 and the original OIICS structure, which was used from 1992 to 2010, BLS advises against making comparisons of the case characteristics from 2011 forward to prior years. More on OIICS can be found here: https://www.bls.gov/iif/definitions/occupational-injuries-and-illnesses-classification-manual.htm.

SOII and CFOI use five classifications to describe each incident that led to a serious nonfatal injury or illness or a fatal injury:

• Nature of injury or illness—the physical characteristics of the disabling injury or illness, such as cuts and lacerations, fractures, sprains and strains, or electrocution
• Part of body affected—the part of body directly linked to the nature of injury or illness cited, such as finger, arm, back, or body systems
• Event or exposure—the manner in which the injury or illness was produced or inflicted, such as caught in running equipment; slips, trips, or falls; overexertion; or contact with electrical current
• Primary source—the object, substance, exposure, or bodily motion that was responsible for producing or inflicting the disabling condition, such as machinery, ground, patient, or electrical wiring
• Secondary source—the object, substance, or person, if any, that generated the source of injury or illness or that contributed to the event or exposure, such as ice or water that contributed to a fall

Exhibit 1 is an illustrative example of how SOII may use OIICS codes to describe the case circumstances of an injury or illness incident:

• Nature: 1311 Amputation
• Part: 4420 Finger(s), fingernail(s), unspecified
• Event: 6410 Caught in running equipment or machinery, unspecified
• Primary source: 3560 Presses, except printing, unspecified
• Secondary source: 9110 Clothing, unspecified

Industry

From 1992 to 2002, SOII and CFOI used the 1987 Standard Industrial Classification (SIC) system to define industry. Despite periodic updates to the SIC system, increasing criticism led to the development of a new, more comprehensive system that reflects more recent and rapid economic changes. Many industrial changes were not accounted for under the SIC system, such as recent developments in information services, new forms of health care provision, expansion of the services sector, and high-tech manufacturing.

The North American Industry Classification System (NAICS) was adopted to define industry beginning with the 2003 reference year. Because of the substantial differences between NAICS and the SIC system, the results by industry in 2003 constitute a break in series. NAICS 2002 was used to define industry for reference years 2003–08; NAICS 2007 was used to define industry for reference years 2009–13; NAICS 2012 was adopted to define industry starting with the 2014 reference year. Users are advised against making comparisons between industry data for 2003 forward and the industry data for previous years. Note that the change from NAICS 2007 to NAICS 2012 resulted in a break in series among industry-level estimates from SOII; however, no series break resulted for the CFOI data. More details on the current NAICS classification as it is used in the IIF programs are below. You can also find a timeline with the details of which coding structures are used for which year in the history section.

North American Industry Classification System (NAICS)

NAICS was developed in cooperation with Canada and Mexico to replace the SIC system, and it was one of the most profound changes for statistical programs focused on measuring economic activities. NAICS uses a process-oriented conceptual framework to group establishments into industries according to the activity in which they are primarily engaged. Establishments using similar raw material inputs, similar capital equipment, and similar labor are classified in the same industry. In other words, establishments that do similar things in similar ways are classified together.

NAICS provides the means to ensure that SOII and CFOI statistics accurately reflect changes in a dynamic U.S. economy. The downside of this change is that these improved statistics resulted in time series breaks due to the significant differences between SIC and NAICS. Every sector of the economy was restructured and redefined under NAICS. A new Information sector combined communications, publishing, motion picture and sound recording, and online services, recognizing our information-based economy. NAICS restructured the manufacturing sector to recognize new high-tech industries. A new subsector was devoted to computers and electronics, including reproduction of software. Retail trade was redefined. In addition, eating and drinking places were transferred to a new accommodation and food services sector. The difference between the retail trade and wholesale trade sectors is now based on how each store conducts business. For example, many computer stores were reclassified from wholesale to retail. Nine new service sectors and 250 new service-providing industries were recognized with the adoption of NAICS in 2003.

NAICS uses a 6-digit hierarchical coding system to classify economic activities into 20 industry sectors—4 sectors are mainly goods-producing sectors, and 16 are entirely service-providing sectors. The 6-digit hierarchical structure of NAICS 2012 allowed for the identification of 1,065 industries. NAICS is revised on a 5-year cycle to reflect changes in the economy, resulting in new standards for 2007 and 2012. These changes were incorporated into SOII and CFOI industry data 2 years later, for 2009 and 2014 respectively. These changes resulted in a series break for SOII industry data from 2013 to 2014, and footnotes should be consulted to check for incompatibility in other cases. For additional information regarding differences between NAICS 2002, NAICS 2007, and NAICS 2012, visit the U.S. Census Bureau NAICS webpage. See the presentation section for more information on the series.

The following list identifies the individual goods-producing and service-providing industry sectors according to NAICS 2012 classifications:

Goods-producing NAICS industry sectors:

• Agriculture, forestry, fishing and hunting (NAICS 11)
• Mining (NAICS 21)
• Construction (NAICS 23)
• Manufacturing (NAICS 31–33)

Service-providing NAICS industry sectors:

• Wholesale trade (NAICS 42)
• Retail trade (NAICS 44–45)
• Transportation and warehousing (NAICS 48–49)
• Utilities (NAICS 22)
• Information (NAICS 51)
• Finance and insurance (NAICS 52)
• Real estate and rental and leasing (NAICS 53)
• Professional, scientific, and technical services (NAICS 54)
• Management of companies and enterprises (NAICS 55)
• Administrative and support and waste management and remediation services (NAICS 56)
• Education services (NAICS 61)
• Health care and social assistance (NAICS 62)
• Arts, entertainment, and recreation (NAICS 71)
• Accommodation and food services (NAICS 72)
• Other services (except public administration) (NAICS 81)
• Public administration (NAICS 92)

In addition to these NAICS sectors, SOII and CFOI statistics are tabulated for several additional NAICS aggregations that are unique to BLS, including the following:

• Natural resources and mining—combining agriculture, forestry, fishing and hunting (NAICS 11), and mining (NAICS 21)
• Trade, transportation, and utilities—combining wholesale (NAICS 42) and retail trade (NAICS 44–45), transportation and warehousing (NAICS 48–49), and utilities (NAICS 22)
• Financial activities—combining finance and insurance (NAICS 52) and real estate and rental and leasing (NAICS 53)
• Professional and business services—combining professional, scientific, and technical services (NAICS 54); management of companies and enterprises (NAICS 55); and administrative and support and waste management and remediation services (NAICS 56)
• Education and health services—combining education services (NAICS 61) and health care and social assistance (NAICS 62)
• Leisure and hospitality—combining arts, entertainment, and recreation (NAICS 71) and accommodation and food services (NAICS 72)

Residential construction industries include residential building construction industries (NAICS 2361) as well as additional specialty trade contractors that BLS added during the implementation of the NAICS.

These special trade contractors (NAICS 238) have a residential/nonresidential element that is unique to BLS:

The Bureau of Labor Statistics will attempt to provide further industry detail in NAICS by adding 19 industries in subsector 238, specialty trade contractors. These additional industries will provide data, where available, about residential and nonresidential contractors. Some of the new industries will include residential and nonresidential roofing contractors, and residential and nonresidential electrical contractors.^⁠2

The 19 industries are:

• 238110 Poured concrete foundation and structure contractors
• 238120 Structural steel and precast concrete contractors
• 238130 Framing contractors
• 238140 Masonry contractors
• 238150 Glass and glazing contractors
• 238160 Roofing contractors
• 238170 Siding contractors
• 238190 Other foundation, structure, and building exterior contractors
• 238210 Electrical contractors and other wiring installation contractors
• 238220 Plumbing, heating, and air-conditioning contractors
• 238290 Other building equipment contractors
• 238310 Drywall and insulation contractors
• 238320 Painting and wall covering contractors
• 238330 Flooring contractors
• 238340 Tile and terrazzo contractors
• 238350 Finish carpentry contractors
• 238390 Other building finishing contractors
• 238910 Site preparation contractors
• 238990 All other specialty trade contractors

Occupation

From 1992 to 2002, the program used the U.S. Census Bureau (BOC) occupational classification system. Beginning with the 2003 reference year, SOII and CFOI began using the Standard Occupational Classification (SOC) system to define occupations. Due to the substantial differences between the SOC and BOC systems, the results by occupation for 2003 constitute a break in series. Users are advised against making comparisons between occupation data for 2003 forward and the occupation data for previous years. More information on BOC can be found on the Census website. More information on SOC can be found on the SOC homepage. Please note that SOII and CFOI used the 2000 SOC to classify occupation data for years 2003–10 and uses the 2010 SOC for years 2011 forward. More details on the current SOC classification as it is used in the IIF programs is below.

Standard Occupational Classification (SOC)

Beginning with the 2011 reference year, CFOI and SOII began using the 2010 SOC system for coding occupations. Before 2011, the 2000 SOC for occupations was used. While the changes to the new structure (SOC 2010) were not extensive, comparisons of SOC 2000 and SOC 2010 occupations should be made with caution.

The 2010 SOC system classifies workers at four levels of aggregation:

• Major group
• Minor group
• Broad occupation
• Detailed occupation

All occupations are clustered into one of 23 major groups, within which are 97 minor groups, 461 broad occupations, and 840 detailed occupations. Occupations with similar skills or work activities are grouped at each of the four levels of hierarchy to facilitate comparisons. For example, life, physical, and social science occupations (19-0000) is divided into four minor groups: life scientists (19-1000), physical scientists (19-2000), social scientists and related workers (19-3000), and life, physical, and social science technicians (19-4000). Life scientists contains broad occupations such as agriculture and food scientists (19-1010), and biological scientists (19-1020). The broad occupation biological scientists includes detailed occupations such as biochemists and biophysicists (19-1021) and microbiologists (19-1022).

Each item in the hierarchy is designated by a six-digit code. The first two digits of the SOC code represent the major group; the third digit represents the minor group; the fourth and fifth digits represent the broad occupation; and the detailed occupation is represented by the sixth digit. Major group codes end with 0000 (e.g., 33-0000, protective service occupations), minor groups end with 000 (e.g., 33-2000, fire fighting workers), and broad occupations end with 0 (e.g., 33-2020, fire inspectors). (The zeros are not always printed.) All residuals ("other," "miscellaneous," or "all other"), whether at the detailed or broad occupation or minor group level, contain a 9 at the level of the residual. Detailed residual occupations end in 9 (e.g., 33-9199, protective service workers, all other), broad occupations that are minor group residuals end in 90 (e.g., 33-9190, miscellaneous protective service workers), and minor groups that are major group residuals end in 9000 (e.g., 33-9000, other protective service workers):

33-0000 protective service occupations

     33-9000 other protective service workers

          33-9190 miscellaneous protective service workers

               33-9199 protective service workers, all other

Race and ethnicity standards

Both the Census of Fatal Occupational Injuries (CFOI) and the component of the Survey of Occupational Injuries and Illnesses capturing case circumstances and worker characteristics were implemented in 1992, following recommendations of a National Academies of Science review highlighting the need to capture detailed case circumstances and worker characteristics for fatal and nonfatal workplace incidents, respectively. At their inception, each of these series used separate methods to categorize the race or ethnicity of injured or ill workers. For example, SOII categorized Hispanic workers separately, while CFOI categorized Hispanic workers by race (e.g., Black or White) and also provided a total count of Hispanic workers. The remaining race and ethnicity categories for both series were:

• White
• Black
• Asian or Pacific Islander
• American Indian or Native Alaskan

The classification of workers by race and ethnicity for CFOI and SOII is based on the 1997 Standards for Federal Data on Race and Ethnicity as defined by the Office of Management and Budget.

In 1999, CFOI amended race categories so that Hispanic workers no longer counted as a race, but solely as an ethnicity. Three additional changes were also incorporated to race and ethnicity categories:

• Asian became a separate category
• Native Hawaiian was combined with Pacific Islander to form a new category, Native Hawaiian or Pacific Islander
• Multirace was added

In 2002, SOII incorporated these same race categories. One result of this revision is that individuals may be categorized in more than one race or ethnic group. Race and ethnicity is one of the few data elements that are optional in SOII. This resulted in 40 percent of the cases involving days away from work for which race and ethnicity were not reported in the 2016 SOII.