Handbook of Methods

U.S. BUREAU OF LABOR STATISTICS

Survey of Occupational Injuries
and Illnesses
The Injuries, Illnesses, and Fatalities (IIF) program provides annual
information on the incidence rate and number of work-related injuries,
illnesses, and fatal injuries, and how these statistics vary by incident, industry,
geography, occupation, and other characteristics. The Survey of Occupational
Injuries and Illnesses (SOII) is an establishment-based survey used to
estimate incidence rates and counts of workplace injuries and illnesses. It
also provides detailed case and demographic data for cases that involve one
or more days away from work (DAFW) and for days of job transfer and
restriction (DJTR) for select industries.
The Handbook of Methods also provides information on the Census of Fatal
Occupational Injuries (CFOI), available at https://www.bls.gov/opub/hom/cfoi/
home.htm. CFOI collects and publishes a complete count of work-related fatal
injuries and descriptive data on their circumstances.
Quick Facts: Survey of Occupational Injuries and Illnesses
Subject areas

Workplace injuries, illnesses, and fatalities

Key measures

Days away from work, Nonfatal workplace injuries &
illnesses incidence

How the data are
obtained

Survey of businesses

Classification system

Demographic, Industry, Occupation

Periodicity of data
availability

Annual

Geographic detail

National, State

Scope

Private sector, State and local government

Key products

Program webpage

• Employer-Reported Workplace Injuries and
Illnesses news release
• Employer-Reported Workplace Injuries and
Illnesses charts package
• State data
• Days of Job Transfer or Restriction Pilot Study

https://www.bls.gov/iif/home.htm

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Table of Contents
CONCEPTS .....................2
DATA SOURCES............14
DESIGN..........................17
CALCULATION...............19
PRESENTATION ............24
HISTORY........................29
MORE INFORMATION...33

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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

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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

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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.

Table 1: Scope of covered incidents in CFOI and SOII
Characteristic
Collection method

Uses multiple source documents (e.g., death
certificates, workers’ compensation reports, and
media reports) to substantiate each case, ensuring
a census.

CFOI

SOII
Uses a sample of approximately 230,000
establishments to generate detailed estimates.
Mandatory survey from BLS for private sector
establishments.(1)

Geographic scope

Data are collected from each state, the District of
Columbia, New York City, Puerto Rico, the U.S.
Virgin Islands, and Guam.

Data are collected from participating states, the
District of Columbia, Puerto Rico, the U.S. Virgin
Islands, and Guam.(2)

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Table 1: Scope of covered incidents in CFOI and SOII
Private sector
workers

Included

Included

Government
workers

Includes federal, state, local, foreign, and other
government workers

Includes state and local workers since 2008
uniformly across the nation(3)

Self-employed

Included

Not included(4)

Volunteer workers

Included(5)

Varies(6)

Agriculture,
forestry, fishing
and hunting

Included

Agriculture establishments (NAICS 111 and 112) with
more than 10 employees(7)

Mining

Included

Included(8)

Railroad

Included

Included(9)

Treatment of
temporary
workers

Coded to the industry in which they are directly
employed(10)

Coded to the industry in which they were injured

All included

Private households, Postal workers (NAICS 491),
space research and technology (NAICS 927), and
national security and international affairs (NAICS
928) not included (11)

Not included

Included

All

All

Included

Included(12)

Specific industries
Illnesses
Age of workers
included
Cases that occur
in territorial waters

Footnotes:
(1) Government establishments are not necessarily required by law to respond. “For State and local government employers, your
State laws determine whether (SOII) is mandatory.” https://www.bls.gov/respondents/iif/faqs.htm#17.
(2) Data for nonparticipating states are collected and used solely for the tabulation of national estimates.
(3) SOII does not cover workers regulated by other federal agencies, 29 U.S.C. § 653(b)(1) (2011) For example, mines regulated
by the Mine Safety and Health Administration or rail transportation firms regulated by the Federal Railroad Administration, nor
does it cover federal workers per 29 U.S.C. § 652(5) (2011).
(4) Self-employed workers are not covered by the Occupational Safety Act of 1970. https://www.osha.gov/pls/oshaweb/
owadisp.show_document?p_table=STANDARDS&p_id=12775.
(5) See Census of Fatal Occupational Injuries (CFOI): Definitions, https://www.bls.gov/iif/oshcfdef.htm and Fatal Occupational
Injuries to Volunteer Workers, 2003–2007 (Gunter, 2010).
(6) Different state OSHA plans may cover volunteers. For more information on if a state covers volunteers, please contact the
respective state OSHA office. National OSHA regulations do not cover volunteer workers, please see 29 C.F.R. § 1904(31)(a)
(2013). See also: http://webapps.dol.gov/elaws/osha/recordkeeping/05.aspx.
(7) The “small agriculture” exclusion is due to a recurring appropriations rider for OSHA that exempts agricultural operations
employing 10 or fewer employees from the 1970 OSH Act in its entirety, including mandatory response to the BLS annual survey
(Pollack and Gellerman Keimig, 1987: 19). See for example, OSHA Directive CPL-02-00-051.
(8) Mining data are collected by the Mine Safety and Health Administration (MSHA) and are provided to SOII for inclusion in the
estimates.
(9) Railroad data are collected by the Federal railroad Administration (FRA) and are provided to SOII for inclusion in the
estimates.
(10) Starting in 2011, CFOI began collecting information on contractors and now temporary workers are coded to their directly
employed industry as in the past, but also the industry to which they were fatally injured in as well, contractor industry. For more
information on contractor data in CFOI see: https://www.bls.gov/iif/oshcfdef.htm.
(11) Though technically no longer excluded from coverage under the Occupational Safety and Health Act of 1970 due to
amended language in the 1998 Postal Employees Safety Enhancement Act, BLS has not yet modified SOII to include the U.S.
Postal Service. See, for example: https://www.osha.gov/Other_Docs/USPS/USPS.html.
(12) Cases that occur in territorial waters within 3 nautical miles from the general coastline or 9 nautical miles (3 leagues) from
Texas, Florida, and Puerto Rico are included. For additional rules including if the vessel is attached to the seabed see: https://
www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=29408.

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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/
oshoiics.htm.

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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

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• 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 serviceproviding industries were recognized with the adoption of NAICS in 2003.

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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 5year 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)

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• 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

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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

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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.

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NOTES

[1] See Automated Coding of Worker Injury Narratives, https://www.bls.gov/osmr/pdf/st140040.pdf.
[2] An excerpt from James A. Walker and John B. Murphy, “Implementing the North American Industry
Classification System at BLS,” Monthly Labor Review,” December 2001, p. 18, https://www.bls.gov/opub/
mlr/2001/12/art2full.pdf.
Last Modified Date: July 16, 2018

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Data Sources
Although SOII began as a mail-based survey, most of the SOII data are now collected electronically. Data
collection methods for SOII have evolved significantly in recent years in response to BLS goals to collect data
more efficiently and to provide more timely and accurate data to its users. Expanded use of available
technologies—namely the Internet and other electronic resources as alternative means for responding to SOII—
has reduced data collection and processing times. The result has been more timely publication of SOII
estimates.
Establishments selected to participate in SOII are notified by BLS in writing in advance of the year for which
they will be required to provide data. This notification process ensures that even those establishments not
normally required by OSHA to maintain injury and illness logs and case forms will do so for the survey year.
Employers then receive instructions on how to record and report their injury and illness experience from state
agencies, or the BLS itself in nonparticipating states, early in the year following the year which they are required
to record. These packets arrive via mail, but the instructions recommend electronic submission.
Employers have the following options available to meet their requirement to respond to SOII:
• Internet. The Internet Data Collection Facility (IDCF) is a centralized platform used by SOII and other BLS
programs. The IDCF provides a uniform, manageable, and secure environment for BLS survey collection
via the Internet. BLS first used the IDCF for the 2002 survey year. The IDCF survey instrument is a Webbased tool that provides sampled employers the ability to respond to SOII online. Employers can enter
their injury and illness data, along with employment and hours worked, using an Internet-based system
that is designed to resemble as closely as possible the hard copy survey forms that employers
traditionally received and responded to by mail. Approximately 73 percent of responses to the 2014 SOII
were submitted via the IDCF.
• Fax form. Employers may request a standardized fax form that they can complete and fax back to BLS.
• Telephone. Employers may call a SOII representative and report their data over the phone.
• Mail. Employers may elect to receive and report their data using a hard-copy, paper survey form that is
mailed to them and returned via mail to BLS.
Survey responses received by mail, fax, or telephone are manually keyed into the SOII data collection system.
Internet responses remove this manual processing because data are entered directly by the employer in the
IDCF and then uploaded into the SOII data collection system. Therefore, Internet responses reduce processing
time and remove the risk of errors associated with the manual keying of data required of SOII responses
received in hard copy format (e.g., mail or fax). Electronic reporting options may also include in-line edits that
assist respondents or immediately identify erroneous data that can be corrected by respondents before
submitting their data. All responses, regardless of which reporting option was used, are electronically edited.
Responses that do not meet the computer screening criteria or pass senior staff review are subsequently
verified with the employer.
Regardless of which option an employer chooses for responding to SOII, each form has been designed to
resemble employer OSHA recordkeeping forms to allow for easy transcription.

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The SOII data collection form is organized into distinct sections, as follows:
• Section 1: Establishment information
This section asks employers to provide basic information about their establishment, including the number
of employee hours worked (needed in the calculation of incidence rates) and the reporting unit’s average
annual employment.
• Section 2: Summary of work-related injuries and illnesses
This section asks employers to summarize the number of injuries and illnesses incurred by employees at
their establishment, as well as the type of injury and illness cases that occurred. These data can be
copied directly from employer injury and illness logs.
• Section 3: Reporting cases
This section asks employers to provide detailed information on the worker and the circumstances of the
injury or illness for cases that resulted in at least 1 day away from work or, for cases that resulted in job
transfer or restriction for selected industries participating in the days of job transfer or restriction (DJTR)
pilot study. These worker and case details can be copied from the employer’s OSHA case forms. State
agency and BLS personnel review the summary data (section 2) and codify the details for the cases
reported in this section (see discussion of OIICS in the concepts section) of serious cases (section 3),
verifying and correcting apparent inconsistencies by contacting the employer again.
• Section 4: Contact information
This section asks employers to provide contact information for the individual who completed the survey
form in case there are discrepancies in the reported data that require correction.
• Section 5: If you need help …
This section provides employers with contact phone numbers within each state should they have
questions or require assistance in completing the survey form.
Every year, by midsummer, the active data collection phase of SOII is completed and the preparation of data for
both national and state estimates of nonfatal occupational injuries and illnesses begins. Estimates of the
incidence rates and counts of employer-reported injuries and illnesses by detailed industry and type of case are
published in late-October. A subsequent release in November provides estimates on the details of the case
circumstances and worker characteristics for injuries and illnesses that involved days away from work.
Mining data are collected by the Mine Safety and Health Administration (MSHA), and railroad data are collected
by the Federal Railroad Administration (FRA), which are then provided to SOII for inclusion in the estimates.

Confidentiality
All data collected in the SOII are subject to the BLS confidentiality requirements that prevent the disclosure of
identifying information. Data collected from SOII are used solely for statistical purposes. All BLS employees and
the state grant agency partners who work with the SOII data take an oath of confidentiality and are subject to
fines and imprisonment for improperly disclosing information provided by respondents. Confidentiality
certification training is required annually.
At BLS, the data are processed and stored on secure servers, with access limited to employees having security
clearances.

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Last Modified Date: November 03, 2017

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Design
A two-stage process is used to select a sample from which estimates are generated for the Survey of
Occupational Injuries and Illnesses (SOII). The first stage involves the selection from a frame that is compiled
from multiple sources, primarily the Quarterly Census of Employment and Wages (QCEW). The frame includes
all in-scope establishments that will be required to participate in SOII (i.e., sample units). The units are selected
to create a stratified sample that takes into account industry, ownership, and establishment size. The second
stage is the selection of sample cases involving days away from work and sample cases involving job transfer
or work restriction from the establishments that have been selected. All cases involving days away from work
are collected from most establishments. However, as a way to reduce respondent burden, establishments that
have a large number of cases involving days away from work are instructed to report a subsample of their cases
that occurred in specified time periods. Cases involving job transfer or work restriction are collected from
establishments in select industries.
Because SOII is a federal–state cooperative program and the data are designed to meet the needs of the
states,1 an independent sample is selected for each participating state or U.S. territory.2 The sample is selected
to represent all in-scope private industries, state government, and local government. The sample size for SOII is
dependent upon the:
•
•
•
•
•

number and kind of cases for which estimates are needed
industries for which estimates are desired
characteristics of the population being sampled
target reliability of the estimates
survey design employed.

One criterion of the SOII design is identifying target estimation industries (TEIs). TEIs, which are selected by
each state, are North American Industry Classification System (NAICS) industries or groups of industries for
which a state wishes to produce an estimate. For example, a state may select to target estimates for hospitals
(NAICS 622). This TEI would include establishments in general medical and surgical hospitals (NAICS 622110),
psychiatric and substance abuse hospitals (NAICS 622210), and specialty hospitals, except psychiatric and
substance abuse (NAICS 622310). A sampling cell is defined by state, ownership, TEI, and size class for which
an estimate will be tabulated. Size classes are based on an establishment’s average annual employment, as
defined below:
•
•
•
•
•

Size class 1 = establishments with 1–10 employees
Size class 2 = establishments with 11–49 employees
Size class 3 = establishments with 50–249 employees
Size class 4 = establishments with 250–999 employees
Size class 5 = establishments with 1,000 or more employees

In SOII, the variability of the incidence rate for total recordable cases (TRC) of injuries and illnesses is used as
the primary variable for determining allocation of the sample, because there is a high correlation between these
cases and other important characteristics of the data being estimated. Historical TRC rates by state are used to

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calculate the variance. The optimal allocation procedure distributes the sample to the industries in a manner
intended to minimize the variance of the total number of recordable cases in the universe or, alternatively, the
incidence rate of recordable cases in the universe. In strata with higher variability of the data, a larger sampling
is selected. For some sampling cells, it is necessary to select all frame units in the cell in order to meet minimum
sampling requirements or to ensure that an adequate number of units are sampled to produce accurate and
reliable estimates for the cell.
Once sampling is complete and all necessary reviews and adjustments have been made, sampling weights are
calculated for units selected in each sampling cell. A maximum weight threshold is applied to sample units.
Sampling weights are calculated by dividing the number of frame units in the sampling cell by the number of
sample units in that cell as follows:

where:
NU = the number of frame units available for selection in the sampling cell
nS = the number of units sampled.
For example, if there are 100 frame units in a sampling cell from which 5 units are selected for the sample, then
the weight assigned to each of the sample units would be 100 divided by 5, or 20.

NOTES
1

Contact information for SOII state partners is available at https://www.bls.gov/iif/oshstate.htm.

2

Data for nonparticipating states are collected by BLS regional staff. Data for these states are used in tabulation of national

estimates; however, state-level estimates are not available separately for nonparticipating states.

Last Modified Date: November 03, 2017

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Calculation
Nonfatal workplace injury and illness data collected for the Survey of Injuries and Illnesses (SOII) are used to
tabulate estimates for two separate data series—annual summary (industry-level) estimates and more detailed
case circumstance and worker characteristic estimates for cases that involved days away from work. Part of the
estimation process involves weighting sample units and cases to represent all injuries and illnesses from units
on the frame from which the sample was selected. Sample unit, case weighting, and calculation of incidence
rates are described in the sections that follow.

Weighting for summary estimates
By means of a weighting procedure, sample units represent all units in their state, industry, employment size
class, and ownership (private sector, state government, or local government), also referred to as a sampling
cell. An original summary weight (OSW) for each sample unit is determined by the inverse of the sampling ratio
(number of units selected relative to the number of frame units available for selection) for the sampling cell from
which the unit was selected. (See example in SOII sample design section.)
Prior to the tabulation of summary estimates, the original summary weight for a sample unit is adjusted by
numerical factors to account for nonresponse from some sample units, benchmarking the sampling frame to the
current survey year, and the occasional inability for some sample units to report data for the unit as it was
sampled. A final summary weight (FSW) used in the tabulation of estimates is determined by applying these
factors to the original weight:
Unit nonresponse adjustment factor (UNRAF). Because a small proportion of SOII participants do not respond,
weights of responding employers in a sampling cell are adjusted to account for nonrespondents by applying a
unit nonresponse adjustment factor.
Outlier adjustment factor (OAF). An OAF is applied when an establishment experiences a rare circumstance
that makes its case count or hours worked unrepresentative of its sampling cell. Including such data with the
original sampling weight would have an undue influence on the estimates. For example, an establishment
reports an unusually high number of illness cases and comments that these were the result of a severe and
uncommon scabies outbreak. The outlier adjustment factor adjusts the unit’s weight to 1 to avoid an
overrepresentation of this uncommon occurrence. An adjustment factor to distribute the remaining weighted
employment of the outlier unit is also applied to each of the remaining useable units in the sampling cell.
Benchmark factors (BMF). The sample for a particular survey year must be drawn prior to that year, so that
selected establishments may be prenotified of their obligation to maintain logs throughout the year. As a result,
the universe file from which the sampling frame was developed is not current to the reference year of the survey,
making it necessary to adjust the data before publication to reflect current employment levels. This procedure is
known as benchmarking. For the SOII, all estimates of totals are adjusted by benchmark factors at the state,
industry, and ownership level, and at the national, industry, and ownership level as well. The benchmarking
procedure requires a source of accurate employment data which can be converted into annual average

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employment figures at the industry level for which separate estimates are desired. The SOII uses employment
data primarily derived from the BLS Quarterly Census of Employment and Wages.
Reaggregation factor (REAG). Because there are occasional instances when a sample unit may be unable to
report data for the unit as it was sampled, adjustments are made to account for these situations by applying a
reaggregation factor to the unit’s original summary weight. For example, a sample unit that was involved in a
merger may report data covering both the original sample unit and the unit or units with which it merged,
requiring an adjustment to the weight to account for the additional unit(s) included in the reported data.
Therefore, the final summary weight for a sample unit is determined by the product of the original summary
weight and these four adjustment factors, or:
FSW= OSW x UNRAF x OAF x BMF x REAG
where:
FSW = Final summary weight
OSW = Original summary weight
UNRAF = Unit nonresponse adjustment factor
OAF = Outlier adjustment factor
BMF = Benchmark factor
REAG = Reaggregation factor

Weighting for case and demographic estimates
This applies to SOII cases involving days away from work (DAFW). Each case involving days away from work is
weighted by the respective sample unit’s final summary weight with which it is associated. In addition, the final
summary weight that is applied to each case is adjusted for several factors to ensure that the number of usable
cases that have been submitted are equal to the days away from work cases used in the tabulation of summary
estimates. These factors are used to adjust for case subsampling (See section on the SOII sample design for
discussion of subsampling.) and case nonresponse for those establishments that did not provide information on
all cases involving days away from work which occurred in their establishment in the survey year.
Case subsampling factor (CSSF). At the establishment level, the CSSF is applied to adjust for instances in
which the number of usable days away from work (DAFW) case forms that are submitted differ from the number
of DAFW cases that are reported on the summary. For example, 39 DAFW cases are reported on the sample
unit’s summary, but 15 case forms are submitted and used, to minimize the burden on the respondent. This

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CSSF is designed to weight the number of DAFW cases for which usable data were reported to equal the total
number of DAFW cases indicated on the summary (that is, the number of DAFW cases that the establishment
experienced). A maximum threshold is applied to this factor, beyond which further adjustments are
accomplished through other factors described below. The CSSF is the ratio of DAFW cases reported on the
summary to the number of DAFW cases for which data were submitted, or

Case nonresponse adjustment factor (CNRAF). This is applied at the sampling cell level. The CNAF is applied
after the CSSF in instances where the CSSF failed to adequately adjust reported summary DAFW cases to
equal the submitted usable DAFW cases for a sampling cell. The CNRAF is designed to adjust for cases that
were not reported as a result of nonresponse within the sampling cell. A maximum threshold is applied to this
factor, beyond which further adjustments are accomplished through the CRAF discussed below. The CNRAF is
calculated as

where:
FSW = Final summary weight
BMF = Benchmark factor
CSSF = Case subsampling factor.
Case ratio adjustment factor (CRAF). This is applied after both the CSSF and CNRAF factors have been applied
but have failed to adjust for missing cases. The CRAF is applied at the estimation cell level (target estimation
industry and size class). The CRAF is calculated as

where:
FSW = Final summary weight
CSSF = Case subsampling factor

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CNRAF = Case nonresponse adjustment factor.

Incidence rate calculation
Incidence rates are calculated using the total case counts obtained through the weighting and benchmarking
procedures described above. The adjusted estimates for a particular characteristic, such as injury and illness
cases involving days away from work, are aggregated to the appropriate level of industry detail. The total is
multiplied by 200,000 for injuries and illnesses combined and for injuries only (that is, 40 hours per week
multiplied by 50 weeks—the base of hours commonly regarded as worked by 100 full-time employees during a
calendar year). The product is then divided by the weighted and benchmarked estimate of hours worked as
reported in the SOII for the industry segment. The formula for calculating the incidence rate is:

Incidence rates for higher levels of industry detail are produced using aggregated weighted and benchmarked
totals. Incidence rates may be computed by industry, employment size, state, various case circumstances, and
select worker characteristics. Incidence rates for illnesses and for case and worker characteristic categories are
published per 10,000 full-time employees, using 20,000,000 hours instead of 200,000 hours in the formula
shown above. (The 20,000,000 hours refers to 10,000 full-time employees working 40 hours per week, 50
weeks per year.) Incidence rates per 10,000 workers can be converted to rates per 100 workers by moving the
decimal point left two places and rounding the resulting rate to the nearest tenth.

Reliability of SOII estimates
Estimates from the SOII are based on a scientifically selected probability sample, rather than a census of the
entire population. (See section on SOII sample design.) Sampling methodology makes it possible to collect data
from a sample from which inferences can be made regarding the characteristics of the population from which
the sample was selected. These sample-based estimates may differ from the results obtained from a census of
the population. The sample used for the SOII was one of many possible samples, each of which could have
produced different estimates. The variation in the sample estimates across all possible samples that could have
been drawn is measured by the relative standard error (RSE), which is used to calculate a confidence interval
around a sample estimate.
The 95-percent confidence interval is the interval centered on the sample estimate and includes all values that
are within 1.96 times the estimate's standard error. If several different samples were selected and used to
estimate a population value (such as injury and illness incidence rates), the 95-percent confidence interval
would include the true population value approximately 95 percent of the time.
To calculate the 95-percent confidence range given an RSE:
1. Divide the RSE by 100 and multiply by the survey estimate to determine the standard error.

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2. Multiply the standard error by 1.96 to determine the confidence error.
3. The survey estimate plus or minus the confidence error is the 95-percent confidence range.
For example, in 2014 the total injury and illness case incidence rate for nursing care facilities (NAICS 6231) was
7.4 cases per 100 full-time workers, with an estimated RSE of 1.2 percent.
1. Divide 1.2 by 100 and multiply by 7.4 for a standard error of 0.0864.
2. Multiply the 0.0864 standard error by 1.96 to get a confidence error of 0.169
3. Hence, we are 95-percent confident that the interval between 7.2 and 7.6 (or 7.4 ± (1.96 × 7.4 ×
0.012)) includes the true value of the incidence rate for total recordable injury and illness cases in
nursing care facilities in 2014.
All estimates derived from a sample survey are subject to sampling and nonsampling errors. Sampling errors
occur because observations are made on a sample, not on the entire population. Percent-relative standard
errors, which are a measure of the sampling error in the estimates, are calculated as part of the SOII estimation
process. Both the estimates and the percent-relative standard errors of the estimates can be found at the
Industry Injury and Illness Data webpage. Relative standard error estimates for case circumstances and worker
characteristic data may be obtained by contacting IIFStaff@bls.gov.
Nonsampling errors in the estimates can be attributed to many sources. Some examples are the inability to
obtain information about all cases in the sample, mistakes in recording or coding the data, or definitional
difficulties. Although not measured, nonsampling errors will always occur when statistics are gathered. To
minimize the nonsampling errors in the estimates, standard procedures are applied to each respondent’s
information. Completed survey forms are automatically reviewed to ensure the consistency and viability of each
case, followed by manual review at the regional and national offices, and apparent inconsistencies are verified
with the employer.
Last Modified Date: November 03, 2017

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Presentation
The presentation of SOII data is released in the fall, and contains two data components. One, sometimes
referred to as the summary, provides estimates of numbers and incidence rates of employer-reported nonfatal
injuries and illnesses at the industry level for all types of cases. A second, sometimes referred to as the case
and demographics release, details case circumstances and worker characteristics for the subset of the cases
that involved days away from work. Prepared tables containing the data can be found for industry data at https://
www.bls.gov/iif/oshsum.htm and for case and demographics at https://www.bls.gov/iif/oshcdnew.htm. A schedule
of releases from the Injuries, Illnesses, and Fatalities program, which includes SOII, can be found at https://
www.bls.gov/iif/osh_nwrl.htm.
Also on the SOII homepages, you will find a chart package, supplemental highlights, quartile incidence rates (for
industries), and special profiles for various topics such as musculoskeletal disorders. For more information on
methodology for calculating rates or a description of the variables collected and coded for SOII, see the
calculation section. All of the rates produced by the SOII program are published online.
In addition to national estimates, state-specific estimates on workplace injuries and illnesses are available for
participating state agencies. A list of state agencies and their telephone numbers is available from BLS at (202)
691-6170 or online at https://www.bls.gov/iif/oshstate.htm. The state page also contains a basic data table for
each state as well as state nonfatal injury rates (for methodology on calculating rates, please see the calculation
section).

Data tools
A variety of tools are available both online and through special request to aid data users. To accommodate the
series breaks in SOII (please see the history section for more information) the online data tools can be run for
the periods 1992–2002, 2003–2010, 2011–2013 (industry data), and 2011 forward (case and demographics)
individually, but cannot cross over these time periods.

Profiles on the Web
The Profiles on the Web system allows users to create customized tables of the number or incidence rate of
work-related nonfatal injuries and illnesses based on user-specified criteria. This is a good way to get an
overview of the data available in an area of interest, both in magnitude and detail.

Databases
There are various ways to obtain very specific data points available from the BLS public database page for
Injuries, Illnesses, and Fatalities at https://www.bls.gov/iif/data.htm. Data users may use a single-screen or
multiscreen data search interface to enter search criteria (both obtain data from the same source and provide
the same types of output). Output data are presented in HTML, text, or Excel formats (per user preference).
Each data point returned is associated with a unique series identifier (ID) and reference period. The series

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identification (ID) is composed of a series of codes associated with various survey classification titles. For
additional information on series IDs, see https://download.bls.gov/pub/time.series/is/ for employer-reported
nonfatal injuries and illnesses at the industry level and https://download.bls.gov/pub/time.series/cs/ (read the .txt
files first).
If you already know the specific series ID that you wish to obtain data for, you may use the series report tool
https://data.bls.gov/cgi-bin/srgate to simply enter the series ID without having to enter search criteria.
You can also find discontinued data series (resulting from the breaks in series) at the bottom of the database
page.

Flat files
Flat files containing all SOII estimates are available through the BLS download server site. Each data series on
the BLS download site includes a two-character series designator. Clicking on the series designator expands
the directory to provide a list of the files included with each series. Included with each series (generally the last
file in each series directory) is a text file that provides: (1) a survey definition and a listing of the FTP files listed
in the survey directory; (2) time series, series file, data file, and mapping file definitions and relationships; (3)
series, data, and mapping file formats and definitions; and (4) a data element directory. The SOII series have
experienced several breaks due to changes in coding systems. Data from these separate series may not be
comparable to one another. Consequently, the following flat file series identifiers cover available SOII data
reflective of these series breaks:
• SOII — Summary data series:
◦ hs — 1976–1988 (1972 SIC)
◦ sh — 1989–2001 (1987 SIC)
◦ si — 2002 (New OSHA recordkeeping)
◦ ii — 2003–2013 (2007 NAICS)
◦ is — 2014 forward (2012 NAICS)

• SOII — Case and demographics data series:
◦ cd — 1992–2001 (1987 SIC)
◦ hc — 2002 (New OSHA recordkeeping)
◦ ch — 2003 forward (2007 NAICS)
◦ cs — 2011 forward (OIICS 2.01)

Special tabulations
Additional data may be available through contacting the SOII program directly. Special data queries with multiple
cross-tabulations for multiple or aggregated years may be run upon request (with some limitations). To request
such data, email iifstaff@bls.gov.

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SOII microdata
SOII data are collected under a pledge of confidentiality and are protected under the Confidential Information
Protection and Statistical Efficiency Act of 2002 (CIPSEA).
BLS allows limited access to SOII microdata for safety researchers and others involved in promoting safety in
the workplace. The microdata are available onsite at the BLS national office in Washington, D.C., or at Federal
Statistical Research Data Centers (FSRDCs) to researchers who agree to protect the confidentiality of the data
and have the safeguards in place to do so. Those seeking to access the microdata must submit a research plan,
and final approval for access rests with the Commissioner of BLS. Proposed projects must have a well-defined
research question of scientific merit that is of a purely statistical nature. More information about obtaining
access to SOII microdata can be found at the BLS restricted data access webpage.

Publications
Articles and detailed tables containing both national and state data are published regularly in the BLS online
publications Beyond the Numbers (BTN), Monthly Labor Review (MLR), The Economics Daily (TED), and other
publications. There are also some articles in the no-longer-published Compensation and Working Conditions
that are accessible on the BLS website through the MLR archive.
You can find a list of some of the articles, as well as special compendiums with both SOII and CFOI data, on the
IIF publications page.
The IIF program also periodically publishes fact sheets relating the data to current events.
Data are also available at https://www.bls.gov/iif/oshcont1.htm and are published in private safety and trade
journals. In addition, state data through 1987 are available on microfiche from the National Technical Information
Service, 5285 Port Royal Road, Springfield, VA 22161. A list of states (including telephone numbers) that can
provide more current state estimates is available from the BLS Office of Safety, Health, and Working Conditions
at (202) 691-6170, or the list can be accessed online at https://www.bls.gov/iif/oshstate.htm.

Data correction
If an error is found in a published SOII data product (news release, data table, etc.), the product is corrected and
republished or incorrect data products are removed. Corrected products will clearly note that a correction was
made. A record of the error is added to the list of BLS errata, and data users who have signed up to receive
notifications from the IIF program are alerted via email. All relevant documentation is updated, and, if
appropriate, new webpages are created to document the error and its correction.

Publication guidelines for SOII estimates
Nonfatal occupational injury and illness estimates were published for more than 1,100 NAICS industries
(including aggregates) in 2014 including select industries within state and local government, which were

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published for the first time for the 2008 survey year. Data for the SOII are collected under a strict pledge of
confidentiality that these data will be used solely for statistical purposes and will not be disclosed for other
purposes. The number of publishable industries may vary from year to year, depending on the number of
industries that fail to meet publication guidelines. Industry estimates may not be published if one of the following
situations exists:
• Publication might disclose confidential information.
• The relative standard error of the estimate for days away from work, job transfer, or restriction cases for
the industry exceeds a specified limit.
• The benchmark factor for the industry falls outside an acceptable range.
Data for an unpublished industry are included in the total for the aggregate industry level of which it is a part.
Also, selected estimates are suppressed within publishable industries if the relative standard error for the
estimate exceeds a specified limit.
For case circumstances and worker characteristics, estimates are rounded to the nearest 10 and are
suppressed if one of the following situations occurred:
• The number of cases is fewer than 15.
• The number of cases is 15 or greater and the relative standard error for the estimate exceeds a specified
limit or if the estimate does not meet confidentiality standards.

Uses and limitations of SOII estimates
National and state policymakers use SOII estimates as an indicator of the magnitude of and trends in
occupational safety and health issues. The Occupational Safety and Health Administration (OSHA) uses the
statistics to help measure the effectiveness of its enforcement and outreach programs in reducing work-related
injuries and illnesses. Private industry labor and management parties use SOII estimates in evaluating safety
programs. Other users include insurance carriers involved in workers’ compensation, industrial hygienists,
manufacturers of safety equipment, researchers, and others concerned with job safety and health.
Many factors can influence counts and rates of injuries and illnesses in a given year. These include not only the
year’s injury and illness experiences but also employers’ understanding of which cases are work-related under
current OSHA recordkeeping guidelines. The number of injuries and illnesses reported in a given year also can
be affected by changes in the level of economic activity, working conditions and work practices, worker
experience and training, and the number of hours worked.
Each year, the SOII measures the number of new work-related illness cases that are recognized and reported.
But some conditions, such as long-term latent illnesses caused by exposure to carcinogens, often are difficult to
associate with the workplace and are not adequately recognized and reported, and therefore are believed to be
understated in the SOII. In contrast, the overwhelming majority of the reported new illnesses are those which
are easier to directly link to workplace activity (such as contact dermatitis or carpal tunnel syndrome).

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SOII estimates have recently come under increased criticism for undercounting all types of workplace injuries
and illness, not just long-term latent illnesses. In 2009, BLS received Congressional funding to investigate this
issue and initiated an ongoing SOII data quality research program. Like the academic research studies that
preceded it, initial BLS research matching SOII data to eligible workers’ compensation records in several states
points to an undercount of injuries and illnesses by SOII. The overall magnitude of the undercount has proven
more difficult to pinpoint. Much of the subsequent research shifted to interviews with employers to learn more
about their injury and illness recordkeeping practices and their understanding of OSHA injury and illness
recordkeeping rules. Initial results of these interviews point to employer misunderstanding of OSHA
recordkeeping rules that could at least partially explain the undercount observed in both academic and early
BLS-funded studies. Recent undercount research has shifted focus into studying the feasibility of collecting
injury and illness data directly from workers. Data collected from workers would avoid errors associated with
employer misreporting and may also be a way to bypass filters to workplace injury and illness reporting that can
cause both workers and employers not to report eligible cases. More information on the SOII data quality
research program can be found at www.bls.gov/iif/undercount.htm.

Data quality research
BLS is conducting ongoing research to investigate the completeness of the injury and illness counts from SOII.
The purpose of this research is to better understand the reasons for an undercount of occupational injuries and
illnesses reported by SOII and to identify ways to improve the collection of occupational injury and illness data.
More information can be found on our Data Quality Research Page.
Last Modified Date: November 03, 2017

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History
Data on safety and health conditions for workers on the job have been produced by the Bureau of Labor
Statistics (BLS) since before World War I. The first safety and health report issued by BLS summarized
industrial accidents in the iron and steel industries in 1912, presenting information on the frequency and severity
of injuries, the occupation of the injured workers, and the nature of their injuries.[1]
Work-related illnesses also were the subject of BLS studies conducted in the early 1900s, such as the
pioneering research on lead poisoning in the workplace done by Dr. Alice Hamilton.[2]
The current BLS Survey of Occupational Injuries and Illnesses (SOII) evolved from annual BLS surveys first
conducted in the 1940s, when injury recordkeeping standards became sufficiently uniform to permit the
collection of nationwide work injury data. Spanning three decades, those nationwide surveys proved useful in
measuring and monitoring injury frequency and severity, but they had two major limitations. First, the survey
data were compiled from and represented only employers who volunteered to record and report work injuries.
Second, work injuries were limited to those that resulted in death, permanent impairment, or temporary
disability, defined as unable to perform regular job duties beyond the day of injury. Thus, survey estimates
excluded many employers and, by definition, numerous cases that required medical treatment (beyond first aid)
or restricted work duties but did not result in days away from work.
These and other limitations were addressed in a landmark piece of safety legislation passed by the U.S.
Congress: the Occupational Safety and Health Act of 1970 (OSH Act). Under the OSH Act Congress delegated
the responsibility for developing a comprehensive statistical system covering work-related injuries, illnesses,
and fatalities in private industry to the BLS. The separation of responsibilities at the national level between data
collection (BLS), regulatory action (OSHA), and safety and health research (CDC/NIOSH) was the original
vision of the OSH Act and still remains our primary operating principle. Our data providers and stakeholders rely
on BLS data being compiled without bias, without regulatory retribution, or without the possibility of
confidentially-collected information being released. Since OSHA and NIOSH use our data for regulatory and
formal advisory purposes, it is important that we remain separate from them to maintain impartiality. The 1970
act and its implementing regulations required that most private industry employers regularly maintain records
and prepare reports on work-related injuries and illnesses, which include all disabling, serious, or significant
injuries and illnesses, whether or not involving time away from work.[3]
In 1972, the BLS, in cooperation with many state governments, designed the Survey of Occupational Injuries
and Illnesses (SOII) to estimate the number and frequency of work-related injuries and illnesses by detailed
industry for the nation and for states participating in the SOII. The data published from the survey continues to
be a great resource to the safety and health community when deciding how to allocate prevention resources
among diverse industries, across which, workers’ risks of injury and illness vary widely.
As originally designed, however, the SOII had limitations. Although the survey identified industries with
dangerous work settings, it failed to produce a reliable count of workplace fatalities. Also, the SOII shed little

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light on worker demographics or the circumstances of an injury or illness. For example, the survey did not ask
about the manner in which an incident occurred and which occupations were involved.
In 1987, a congressionally funded National Academy of Sciences (NAS) study recommended that these
deficiencies be corrected by collecting detailed data on severe, nonfatal occupational injuries and illnesses
reported in the SOII and by compiling complete accounts of occupational fatalities from administrative records,
such as death certificates and workers’ compensation reports.[4] This critical review of the SOII provided the
impetus for the redesign of the SOII and the creation of the Census of Fatal Occupational Injuries (CFOI).
Some of the NAS recommendations suggested using multiple data sources such as death certificates and
workers’ compensation reports to identify and profile fatal work injuries for all workers. More specifically, the
Keystone Dialogue Group recommended the development of a method for counting work-related fatalities,
stating that the "development of an accepted count of workplace deaths should mute controversy on this issue
stemming from the variety of estimates coming from different sources."[5] In this regard, fatality estimates made
by different organizations at that time varied greatly from 3,000 to 11,000 deaths nationally per year.[6]
The CFOI approach to compiling data on fatal work injuries was initially tested in a BLS cooperative effort with
the Texas Department of Health during 1988. That study, which collected fatality data retrospectively for 1986,
highlighted the need for multiple data sources and the feasibility of matching fatalities and their circumstances
across those sources.[7] This approach was tested again in Texas and Colorado in 1990, with results confirming
that the same kind of data could be obtained from multiple data sources on a current basis.[8] The CFOI was
initially implemented in 32 states and New York City in 1991 and expanded to cover all 50 states and the District
of Columbia in 1992. As of 2011, the U.S. territories Puerto Rico, Virgin Islands, Guam, and America Samoa are
also included.
Several changes that have had significant impacts on data from the BLS safety and health statistics program,
including updated recordkeeping requirements, new industry and occupation classification systems, and
changes in race and ethnicity standards, are discussed in the concepts section.

Timeline
The following timeline illustrates key developments in identifying and quantifying the annual number of workrelated injuries, illnesses, and fatalities. Most changes were milestones in program development, such as the
Occupational Safety and Health Act of 1970 and the National Academy of Sciences’ National Research Council
report, while others were fundamentally philosophical, such as the New Deal’s new attitudes toward labor law
and regulation.

Key developments
• 1894: BLS begins publishing extensively on new developments in state and foreign social legislation and
practices, including accident prevention and workers' compensation. In the years preceding World War I,
BLS begins to give special attention to industrial accidents and occupational diseases.

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• 1912: BLS issues its first annual report on injury rates in the iron and steel industry. A few years later,
cooperative arrangements with Massachusetts, New York, and Ohio are established for reporting
industrial accidents; additional states later join the program.
• 1926: BLS introduces an annual survey tracking the frequency and severity of industrial injuries for
several manufacturing industries using data compiled from state records, as well as reports from
establishments in targeted industries. By 1930, BLS data covered a quarter of the workforce in some 30
manufacturing industries.
• 1939: Occupational fatality data are added to the survey.
• WWII (1941-45): BLS publishes monthly injury data for industries of particular wartime importance. After
the war, BLS adds more industries; by 1966, more than 650 industries were included.
• 1970: The Occupational Safety and Health Act of 1970 instituted common definitions and recordkeeping
standards and required employers to maintain accurate workplace injury and illness records.
• 1974: Data from SOII (summary) are first published, for survey year 1972.
• 1987: The National Academy of Sciences’ National Research Council completes a study that leads to a
substantial redesign of the occupational injury, illness, and fatalities statistical program.
(Years below indicate the year of data the change started)
• 1992: BLS restructures the survey to include data on characteristics of injured or ill workers and
circumstances of the specific nonfatal injury or illness involving lost workday cases and launches a
census to capture all fatal occupational injuries. (Modern CFOI and SOII program started)
• 1992: BOC system is used to classify occupation, SIC to classify industry, and original OIICS to code the
case characteristics of injuries illnesses and fatalities.
• 1994: CFOI begins publishing a preliminary report, followed by a revised and final report of occupational
fatalities.
• 1999: CFOI begins collecting and publishing MSA data. (See the CFOI definitions page and the concepts
section for more information.)
• Early 2000s: BLS begins to provide a variety of web-based tools to facilitate reporting and data
dissemination.
• 2001: CFOI begins collecting data on birthplace. (See the CFOI definitions page for more information.)
• 2002: OSHA recordkeeping changes result in SOII series break.
• 2003: SOII and CFOI series break, BLS moves to the Standard Occupation Classification (SOC) system,
2000 edition to code occupations and the North American Industrial Classification System (NAICS), 2002
edition to code industry.
• 2008: SOII begins publishing national estimates for state and local government.
• 2009: SOII and CFOI adopt NAICS 2007 edition, not resulting in a series break.
• 2011: SOII and CFOI series break, BLS moves to the Occupational Injury and Illness Classification
(OIICS) 2.01 to code case characteristics. BLS also adopts SOC 2010 edition definitions. CFOI begins
collecting and publishing data on contracted workers. (See the CFOI definitions page and concepts
section for more information.)
• 2014: SOII and CFOI adopt NAICS 2012 edition. This does not result in a series break for CFOI or SOII—
Case and Demographics, but does result in a series break for SOII—Annual Summary.
• 2015: CFOI discontinues issuing a preliminary data release, and began publishing a single final data
release in December, 4 months earlier than in previous years).
More information on the history of the Injuries, Illnesses, and Fatalities (IIF) program can be found on the IIF
History homepage. For more information on the historical development of occupational injury, illness and fatality

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data, see the articles “Improvements in the BLS safety and health statistical system,” “Occupational safety and
health statistics: new data for a new century,” “A Century-Long Quest for Meaningful and Accurate Occupational
Injury and Illness Statistics,” and “The quest for meaningful and accurate occupational health and safety
statistics”. For more information on the OSHA record keeping changes see the article “Occupational injury and
illness: new recordkeeping requirements”.

NOTES

[1] The Safety Movement in the Iron and Steel Industry, Bulletin 234 (Bureau of Labor Statistics, 1918).
[2] The White-Lead Industry in the United States, Bulletin 95 (Bureau of Labor, 1911).
[3] See section 24(a) of the Occupational Safety and Health Act of 1970 (Public Law 91–596).
[4] See E.S. Pollack and D.F. Keimig, eds., Counting Injuries and Illnesses in the Workplace: Proposals for
a Better System (Washington, National Research Council, National Academy Press, 1987), pp. 103–06.
[5] See the Keystone Center’s final report, "Keystone National Policy Dialogue on Work-Related Illness and
Injury Recordkeeping," (Keystone, CO, January 1989), pp. 47. For an account of various attempts to count
fatalities at work, see Dino Drudi, "The evolution of occupational fatality statistics in the United States,"
Compensation and Working Conditions, July 1995.
[6] See BLS Survey of Occupational Injuries and Illnesses (1972–91); the National Safety Council
Accidents Facts; and the National Institute for Occupational Safety and Health’s National Traumatic
Occupational Fatality Study A Decade of Surveillance, 1980–1989.
[7] See Janice Windau and Donna Goodrich, "Testing a census approach to compiling data on fatal work
injuries," Monthly Labor Review, December 1990, pp. 47–49. The study also found that, for verification
purposes, timeliness is important in maximizing respondents’ recall and in reducing the number of those
failing to respond because they have relocated.
[8] See Guy Toscano and Janice Windau, "Further testing of a census approach to compiling data on fatal
work injuries," Monthly Labor Review, October 1991, pp. 33–36.

Archives
• August 13, 2012
• July 17, 2018
Last Modified Date: July 16, 2018

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More Information
Special topic surveys
In addition to the Survey of Occupational Injuries and Illnesses (SOII) and Census of Fatal Occupational Injuries
(CFOI) products normally produced in any reference year, BLS has conducted, in conjunction with other
governmental agencies, various "special topic" surveys regarding occupational safety and health-related topics.
These special surveys have included the following topics:
•
•
•
•
•

Survey of Respirator Use and Practices
Survey of Workplace Violence Prevention
Employer Interview Survey
Employee/Household Survey
Automated coding

Survey of Respirator Use and Practices
The Survey of Respirator Use and Practices was a special survey of U.S. employers regarding the use of
respiratory protective devices conducted by BLS for the National Institute for Occupational Safety and Health
(NIOSH), Centers for Disease Control and Prevention (CDC). This voluntary survey provided estimates of the
number of establishments and employees who used respirators during a 12-month period by type of respirator
and type of use. The survey also collected data on the characteristics of the respirator program at the
establishment, assessment of medical fitness to wear respirators, characteristics of respirator training at the
establishment, usefulness of NIOSH approval labels and respirator manufacturers’ instructions, substances
protected against by the use of respirators, and fit testing methods used for respirators. Results from this survey
are available at Respirator Use and Practices.

Survey of Workplace Violence Prevention
The Survey of Workplace Violence Prevention was another special survey conducted by BLS for NIOSH. This
survey studied the maintenance of a safe work environment, including the prevalence of security features, risks
facing employees, employer policies and training, and related topics. Data from this survey are available for
private industry and state and local government by industry and size of establishment, where size is measured
by the number of workers employed. Results from this survey are available at https://www.bls.gov/iif/
osh_wpvs.htm.

Employer Interview Surveys
In 2012, BLS partnered with four states to conduct a series of employer telephone interviews with recent SOII
respondents to obtain information on employer injury and illness recordkeeping practices. With its state
partners, BLS worked to develop a standardized survey instrument. States contacted a sufficient number of
employers to generalize the results of the survey to all employers in that particular state. Additional information
on these employer interviews can be found in the 2016 Monthly Labor Review article “An update on SOII
undercount research activities.”

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Results from these employer telephone interviews indicated that many respondents lacked OSHA
recordkeeping knowledge. This lack of knowledge may result in an overreporting of less severe injuries and
illnesses cases, many that did not need to be recorded or reported per OSHA recordkeeping criteria, combined
with an underreporting of more severe injury and illness cases in which the worker missed at least one day
away from work. Detailed analysis of the results of these interviews can be found in the 2016 Joint Statistical
Meeting article “Identifying patterns in employer reporting errors in the BLS Survey of Occupational Injuries and
Illnesses.”
Following the four-state study, BLS partnered with Westat to conduct a nationwide followup survey of 2013 SOII
respondents regarding their injury and illness recordkeeping practices. Initial results from this study point to
similar conclusions, with a lack of respondent knowledge of recordkeeping rules possibly contributing to injury
and illness cases going unrecorded and unreported to BLS.

Employee/Household Survey
In 2014, BLS began to examine the feasibility of collecting occupational injury and illness data directly from
workers to complement the employer-provided data BLS collects via SOII. Research has shown that various
filters, or barriers to reporting, can occur when employers collect and report injuries and illnesses. These
barriers may be mitigated or avoided by contacting workers directly for this information.
Following some initial exploratory research conducted with Westat, BLS worked with NORC to develop and
refine a survey instrument for use in data collection. BLS is using this survey instrument in its work with another
contractor, ICF, to conduct a pilot test to determine the feasibility of collecting occupational injury and illness
data directly from workers. The results of this pilot will inform future BLS decisions regarding the feasibility of a
worker survey.

Automated coding
SOII collects data from sampled establishments on OSHA forms 300 and 301. We use the information provided
on these forms to generate detailed statistics on the characteristics of cases involving injury or illness. Prior to
survey year 2014, BLS exclusively relied on humans to code cases, on the basis of a careful reading and
analysis of the case narrative. In 2014, BLS began using computer assisted coding to code a subset of cases.
For more information on these efforts and results, please see our automated coding page.

Job transfer or work restriction
The Bureau of Labor Statistics is conducting an ongoing pilot study to learn more about occupational injuries
and illnesses that resulted in days of job transfer or work restriction. The purpose of this study is to compare the
case circumstances and worker characteristics of injuries and illnesses that require days away from work to
recuperate and those that lead to days of job transfer or restriction only, without time away from work. The
regular Survey of Occupational Injuries and Illnesses (SOII) includes only data on the case circumstances and
worker characteristics on days-away-from-work cases; this study is an expansion of SOII to collect and report
the same detail for days-of-job-transfer-or-restriction cases.

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The study began with an initial set of six North American Industry Classification System (NAICS) subsectors
collected for data years 2011–13. For data year 2014, case circumstance and worker characteristic data for
days of job transfer or work restriction cases for a different set of industries were collected. Data and additional
information are available at https://www.bls.gov/iif/days-of-job-transfer-or-restriction.htm.

Technical references
Abraham, Katharine G., William L. Weber, and Martin E. Personick, "Improvements in the BLS safety and health
statistical program." Monthly Labor Review, April 1996, pp. 3–12. https://www.bls.gov/opub/mlr/1996/04/
art1full.pdf.
Brown, Jeff. "Nonfatal injuries and illnesses in state and local government workplaces in 2008." Monthly Labor
Review, February 2011, pp. 33–40. https://www.bls.gov/opub/mlr/2011/02/art3full.pdf.
Drudi, Dino. "A century-long quest for meaningful and accurate occupational injury and illness statistics."
Compensation and Working Conditions, winter 1997, pp. 19–27. https://www.bls.gov/opub/mlr/cwc/a-centurylong-quest-for-meaningful-and-accurate-occupational-injury-and-illness-statistics.pdf.
Drudi, Dino. "The quest for meaningful and accurate occupational injury and illness statistics." Monthly Labor
Review, December 2015. https://www.bls.gov/opub/mlr/2015/article/the-quest-for-meaningful-and-accurateoccupational-health-and-safety-statistics.htm.
Northwood, Joyce, Eric Sygnatur, and Janice Windau. “Updated BLS Occupational Injury and Illness
Classification System.” Monthly Labor Review, August 2012, pp. 19–28. https://www.bls.gov/opub/mlr/2012/08/
art3full.pdf.
Toscano, Guy A., Janice Windau, and Dino Drudi. "Using the BLS Occupational Injury and Illness Classification
System as a Safety Management Tool." Compensation and Working Conditions, June 1996, pp. 19–28. https://
www.bls.gov/iif/oshwc/cfar0014.pdf.
U.S. Bureau of Labor Statistics. Corrections to Survey of Occupational Injuries and Illnesses data, 2011 and
2012. https://www.bls.gov/bls/errata/iif_errata_1014.htm.
U.S. Bureau of Labor Statistics. Days of job transfer or restriction pilot study. https://www.bls.gov/iif/days-of-jobtransfer-or-restriction.htm.
U.S. Bureau of Labor Statistics. Monthly Labor Review. Articles on safety and health topics. https://www.bls.gov/
opub/mlr/subject/a.htm.
U.S. Bureau of Labor Statistics. Occupational Injury and Illness Classification System (OIICS) manual, version
2.0, September 2010. Detailed BLS coding structures used to classify workplace injuries resulting in death and

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for nonfatal injuries and illnesses resulting in days away from work, with explanatory article. https://www.bls.gov/
iif/oshoiics.htm
U.S. Bureau of Labor Statistics. Occupational Injuries and Illnesses: Counts, Rates, and Characteristics.
Bulletins issued annually. (Before 1992, Occupational Injuries and Illnesses in the United States by Industry.)
U.S. Bureau of Labor Statistics. Standard Occupational Classification. https://www.bls.gov/soc.
U.S. Bureau of Labor Statistics. Using Survey data to evaluate your firm’s injury and illness experience.
Guidelines to assist employers in comparing their injury and illness experience to others with similar-size
workforces in the same industry. https://www.bls.gov/iif/osheval.htm.
U.S. Bureau of Labor Statistics. Workplace injuries and illnesses, Nonfatal occupational injuries and illnesses
requiring days away from work, and National census of fatal occupational injuries. News releases issued
annually. Available for 1994 forward at https://www.bls.gov/iif.
U.S. Census Bureau. North American Industry Classification System. https://www.census.gov/eos/www/naics/.
U.S. Department of Labor. "Safety and Health in the Workplace." Report on the American Workforce, 1994,
chapter 3.
U.S. Department of Labor. OSHA Injury and Illness Recordkeeping. http://www.osha.gov/recordkeeping/
index.html.
U.S. Occupational Safety and Health Administration. Standard Industrial Classification. http://www.osha.gov/pls/
imis/sic_manual.html.
Wiatrowski, William J. "Occupational safety and health statistics: new data for a new century." Monthly Labor
Review, October 2005, pp. 3–10. https://www.bls.gov/opub/mlr/2005/10/art1full.pdf.
Wiatrowski, William J. “Using workplace safety and health data for injury prevention.” Monthly Labor Review,
October 2013. https://www.bls.gov/opub/mlr/2013/article/using-workplace-safety-data-for-prevention.htm.
Last Modified Date: November 03, 2017

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