This report was supported in part by Cooperative Agreement OS-23109-13-75-J-53 from the US Department of Labor (DOL). 

The contents are solely the responsibility of the authors and do not necessarily represent the official views of the Bureau of 

Labor Statistics and the DOL.

WASHINGTON STATE DEPT. OF LABOR AND INDUSTRIES

SHARP PROGRAM

SOII Undercount Research: 

Washington SOII-WC Record Linkage, 

2000 - 2011

FINAL REPORT

Prepared for the

U.S. Department of Labor, Bureau of Labor Statistics

Through Cooperative Agreement No. OS-23109-13-75-J-53

August 30, 2014

Sara Wuellner, Study Coordinator

Dave Bonauto, Principal Investigator

Darrin Adams, Data Scientist

Washington State Dept. of Labor & Industries

Safety and Health Assessment and Research for Prevention (SHARP) Program

PO Box 44330

Olympia, WA 98501
i 

Contents 

EXECUTIVE SUMMARY ............................................................................................................................ 1

Objectives ........................................................................................................................................... 1

Methods ............................................................................................................................................. 1

Results ................................................................................................................................................ 1

INTRODUCTION ...................................................................................................................................... 3

Research aims of record linkage......................................................................................................... 3

METHODS ............................................................................................................................................... 4

Data Sources ....................................................................................................................................... 4

BLS SOII Case and Demographic Data ............................................................................................ 4

Washington Workers Compensation Data ..................................................................................... 4

Washington Unemployment Insurance Data ................................................................................. 6

Changes in data from 2000 – 2011:................................................................................................ 6

Record Linkage ................................................................................................................................... 8

Establishments excluded from the study ....................................................................................... 8

Identifying BLS participants in Washington workers’ compensation data .................................... 8

Linking BLS cases and Washington workers compensation claims data ........................................ 9

Analysis .............................................................................................................................................11

RESULTS ................................................................................................................................................13

Linkage Results ................................................................................................................................. 13

Trends in Reporting ..........................................................................................................................14

Trends in reporting by workers’ compensation insurer...................................................................15

Trends in reporting by establishment size .......................................................................................19

Trends in reporting by industry ........................................................................................................21

Trends in reporting by injury characteristics ....................................................................................26

Event or exposure leading to the injury .......................................................................................26

Nature of injury ............................................................................................................................29

Multivariate regression ................................................................................................................31

KEY FINDINGS .......................................................................................................................................32

AREAS FOR FUTURE RESEARCH ............................................................................................................32

REFERENCES .........................................................................................................................................33
1 

EXECUTIVE SUMMARY 

Objectives 

This study examines the trend in unreported WC claims to the BLS Survey of Occupational Injuries and 

Illnesses (SOII) between 2002 and 2011 to assess patterns in underreporting by industry and injury 

characteristics over time, adding context to the recent declines observed in the BLS SOII data. 

Methods

Using the UI account and reporting unit numbers provided in the SOII establishment file, we identified 

BLS sampled establishments within Washington’s UI data from the quarter the SOII sample was drawn. 

The sampled establishments were mapped through successive quarters within the UI data to identify 

changes in ownership, physical location, or a break in liability. We then identified individuals employed 

by SOII respondents during the survey year using the UI account information current at the time of the 

survey. Using the social security numbers reported in UI data among SOII-participating UI accounts to 

identify the surveyed workforce, we extracted WC claims among the sampled workforce with an injury 

date in the survey year in which the establishment participated. Research staff developed SAS code to 

deterministically link records through an iterative process, linking SOII cases to WC claims based on: 

worker first name, last name, date of birth or age at injury, and date of injury. 

When the sampled establishment represented one of many reporting units within a UI account, unlinked 

claims among non-sampled units were identified based on discordance between UI and WC employer 

location data. These claims were excluded from the group of unlinked claims and considered not 

reportable to SOII. For sampled establishments that represented the entirety of a UI account, we 

retained all claims among workers whose SSNs were reported in UI for the sampled UI account. 

To reduce claims to injuries that resulted in one or more days of missed work, thus meeting the SOII 

DAFW case criteria, we used WC indemnity payment information. State funded claims that received 

payments for missed work, or self-insured claims classified as eligible for time loss payments were 

considered to have met the missed work criterion to be recordable as a DAFW case. We then used claim 

event dates to indicate whether the missed work occurred within the survey year. 

Generalized linear models were used to assess the trend in reporting over time. Logistic regression 

methods were used to isolate the effect of establishment and injury characteristics on underreporting. 

Results 

Between 2002 and 2011, underreporting ranged from a low of 30.6% of SOII-eligible WC time loss claims 

in 2006 to a high of 38.9% in 2010. During the first five years of the study period (2002 – 2006), 

underreporting was found to decrease annually by an estimated 0.8%. The decrease was followed by an 

increase in underreporting, between 2007 and 2011, of an estimated annual increase of 2.1%. Despite 

the observed increase in underreporting, the total estimated number of SOII-eligible WC time loss 

injuries (based on reported and unreported claims) decreased over the ten year span. 
2 

Claims from establishments in Health Services, Public Administration, Transportation, Educational 

Services, Agriculture, Forestry, Fishing, Construction, Services (other than health, educational and 

social), and Communications, Electric, Gas, Sanitary Services were less likely to be reported compared to 

claims among Manufacturing establishments. Underreporting increased most among Educational 

Services, Transportation, and Health Services. In Wholesale Trade, Manufacturing, and Agriculture, 

Forestry, and Fishing the rate of underreporting did not change over the ten year period. In Retail Trade, 

underreporting decreased. 

Claims for injuries from bodily reaction and exertion were more likely to be unreported compared to 

injuries resulting from falls or injuries from contact with objects and equipment. Underreporting was 

found to increase over time among both injuries from bodily reaction and exertion and injuries for 

contact with objects and equipment, and remained constant for injuries from falls. 

Claims for sprains, strains, tears were more likely to be unreported compared to most other traumatic 

injuries. Non-traumatic diseases, conditions, or disorders were more likely to be unreported compared 

to sprains, strains, tears. Underreporting increased among: Sprains, strains, tears; non-specified 

traumatic injuries; non-traumatic diseases, conditions, disorders. Underreporting increased slightly 

among Fractures and Multiple traumatic injuries in the same ten year time period and did not change 

for Bruises and contusions. 
3 

INTRODUCTION 

The US Bureau of Labor Statistics (BLS) provides annual national and state estimates of nonfatal 

occupational injuries and illnesses based on approximately 230,000 employer reports of OSHA 

recordable cases collected through the Survey of Occupational Injuries and Illnesses (SOII) (US 

Department of Labor, 2012). According to the BLS, SOII is the nation’s largest occupational injury and 

illness surveillance system. 

Increasingly, evidence suggests that the BLS does not accurately estimate the true burden of 

occupational injuries and illnesses through the annual survey of employers, although estimates of the 

BLS undercount vary widely (Boden and Ozonoff, 2008; Leigh et al., 2004; Oleinick and Zaidman, 2010; 

Rosenman et al., 2006). In response to the most recent concerns of underreporting injuries and illnesses 

on employer OSHA logs and in the SOII, the federal government undertook efforts to better understand 

employer recordkeeping. The US Government Accountability Office evaluated OSHA’s audit procedures 

used to verify the workplace injury and illness data collected through OSHA’s Data Initiative (US 

Government Accountability Office, 2009); OSHA initiated a national emphasis program for 

recordkeeping (US Department of Labor, 2009); and BLS supported both intramural and extramural 

research projects to examine the nature of the observed undercount (Ruser, 2010). 

As part of the BLS-sponsored undercount research, the Safety and Health Assessment and Research 

for Prevention (SHARP) Program at the Washington State Department of Labor and Industries (L&I) 

received funding to explore injury and illness reporting through a data linkage project to match twelve 

years of Washington SOII data to Washington workers’ compensation (WC) claims data. 

Research aims of record linkage 

In 2009, BLS funded research to link 2007-2008 SOII data for California establishments and 2006 –

2008 SOII data for Washington establishments to the respective state’s WC claims data in order to 

investigate the underreporting of cases in SOII compared to WC claims data. Both studies found 

underreporting in SOII compared with state workers’ compensation claims data although the estimated 

magnitude of the undercount is difficult to compare due to differences in data availability and the 

methods used to estimate the undercount. Among SOII-eligible Washington WC claims with key claim 

event dates in or shortly after the survey year, an estimated 70% were captured by SOII. One question 

that remained was whether the trend in underreporting was consistent from year to year – and 

especially salient issue in light of the observed trend in declining BLS estimates of occupational injuries 

and illnesses over time. In other words, an increasing undercount from year to year may explain the 

declining BLS rates. 

To evaluate the trend in reporting, BLS funded an additional study in Washington State to link 

twelve years of Washington SOII data to the Washington WC claims data. The aims of the study are to: 

1. Assess annual reporting of injuries and illnesses in SOII compared with WC; 

2. Evaluate whether the trends in reporting differ over time; and 

3. Identify establishment or case characteristics associated with differences in reporting 

trends. 
4 

METHODS 

Data Sources 

BLS SOII Case and Demographic Data 

BLS administers SOII annually in partnership with participating states to estimate the incidence of 

nonfatal OSHA-recordable work-related injuries and illnesses. SOII includes both public and private 

sector employment except for federal employees, private household workers, farms with fewer than 11 

employees, and the self-employed. Each year, establishments are randomly sampled from the 

Longitudinal Establishments Database (LDB) which consists of unemployment insurance (UI) account 

information collected by state employment security agencies.1

Prior to the survey year, BLS mails a letter to sampled establishments instructing them to record all 

injuries and illnesses that occur during the survey year in accordance with OSHA recordkeeping 

regulations. Establishments otherwise exempt from OSHA recordkeeping requirements based on 

industry or employment size are eligible for participation in SOII and are required to maintain OSHA 

injury and illness recordkeeping forms, like the non-exempt establishments, for the duration of the 

survey year. After the survey year has ended, participating establishments provide the BLS with two 

types of injury and illness data: 1. aggregate numbers of OSHA recordable cases and 2. detailed worker 

and incident information on injuries and illnesses occurring in the survey year that resulted in one or 

more calendar days away from work (DAFW) beyond the day of injury. Case reports are then coded to 

classify the event, source, body part, and nature of the reported injury or illness. Based on these 

employer reports, BLS publishes estimates of the total numbers and rates of occupational injuries and 

illnesses. 

To link SOII and WC records, two types of SOII data were obtained: 

1. Establishment files that include characteristics such as industry, size, address, and aggregate 

totals of OSHA recordable injuries that occurred during the survey year; and 

2. The case and demographic data for DAFW injuries and illnesses that includes worker name, 

date of injury, description of the injury, number of days of missed and restricted work, and 

other case characteristics. 

BLS supplied data for Washington establishments for survey years 2000 – 2011. 

Washington Workers Compensation Data 

Washington mandates workers’ compensation insurance for all employers operating in the state 

except those covered by an alternative workers compensation system (e.g. Harbor and Longshore 

worker, Federal workers – Office of Workers Compensation Programs)2

 or are specifically exempt from 

requirements for mandatory insurance as listed in state statute.3 Elective workers compensation 

insurance is available for self-employed workers. 

Washington employers are required to purchase workers’ compensation insurance from the 

Washington State Fund unless they are able to self-insure. The Washington State Fund is administered 

 

1

 Mining and railroad establishments are not sampled from the LDB; instead, injury and illness data in these 

industries are submitted to BLS by MSHA and FRA, respectively. 

2

See Revised Code of Washington, Title 51.12 ‘Employments and Occupations Covered’ 

http://apps.leg.wa.gov/rcw/default.aspx?cite=51.12

3

 Employments excluded from mandatory workers compensation coverage include: the self-employed; family 

members younger than 18 working on family farms; domestic servants; sole proprietors, partners or corporate 

officers; jockeys; newspaper vendors or delivery persons; contract musicians, and insurance brokers. See Revised 

Code of Washington, Title 51.12.020 ‘Employments excluded’ http://apps.leg.wa.gov/rcw/default.aspx?cite=51.12.020
5 

by L&I. Of the approximately 160,000 Washington employer workers’ compensation accounts, 99.75% 

are insured through the State Fund, covering approximately 70% of all workers in the state. The 

remaining workers’ compensation accounts (approximately 400) are self-insured and typically represent 

large employers (e.g. Boeing, Microsoft). Companies must meet specific requirements to self-insure and 

the self-insurance program has significant oversight and reporting requirements to L&I.4

Each employer in Washington State has a workers’ compensation policy. The policy may cover one 

or more accounts, and each account may comprise one or more business locations. Workers 

compensation accounts are associated with the employer’s Uniform Business Identifier (UBI). The UBI is 

a Washington State specific employer identifier that links an employer across state government 

administrative databases (e.g. the Washington State Department of Labor and Industries, the 

Washington State Employment Security Department, and the Washington State Department of 

Revenue). A workers’ compensation policy, account and business location each has an assigned address 

within the workers’ compensation system. 

In Washington, a workers’ compensation claim is initiated by an injured or ill worker seeking medical 

care from a health care provider. The injured worker and health care provider complete a report of 

accident form which is sent to either the state fund or the self-insured employer or the self-insured 

employer’s third party administrator. Differing from many WC systems operating in other states, the 

employer does not initiate a workers compensation claim in Washington, and while a worker is required 

to report an injury to his employer, he may not do so. Regardless, the employer is always notified by L&I 

of a workers compensation claim. The statute of limitations for filing a workers’ compensation claim for 

an occupational injury is one year after the injury.5 For an occupational disease the statute of limitations 

is two years after the written notification from a health care provider for eligibility to file a claim.6 

Workers compensation claims are accepted and rejected as work-related by trained claims 

adjudicators in accordance with Washington State statutes, rules, and case law. Every filed claim is 

retained in the L&I database, whether eligible for wage replacement, accepted for medical-aid only, or 

rejected. Medical treatment, wage replacement benefits and all other billed services are linked to the 

claim identification number and maintained in L&I databases. In Washington, the waiting period for 

wage replacement eligibility is three calendar days after the date of injury. The date of injury is not 

counted towards any part of the waiting period for wage replacement eligibility. If the worker remains 

disabled at 14 days, the first three days of time loss are paid. The number of time loss days paid is

captured in these databases as are employer protests, formal legal appeals by the employer, timing of 

claim adjudication processes (e.g. disability determination, assignment of total permanent disability), 

and employer apportionment of occupational disease. 

Claimant (worker) identifiers include name, date of birth, sex, and social security number. Each claim 

has a date of injury and a date in which the department received the claim (claim established date). 

Claims may be assigned a date of injury based on adjudication and legal proceedings associated with the 

claim. State funded claims also have the date of the first medical visit, the date the claimant was first 

unable to perform the job of injury (disability date), and the date the department made the initial 

payment for wage replacement (first time loss payment date). All compensable claims (State Fund and 

self-insured) are coded for nature of injury, body part, event or exposure, and source according to the 

Occupational Injury and Illness Classification System 2007 (OIICS). Accepted non-compensable State 

Fund claims are also coded; accepted non-compensable self-insured claims are not. 

 

4

See Revised Code of Washington, Title 51.14 ‘Self-Insurers’ http://apps.leg.wa.gov/RCW/default.aspx?cite=51.14 

5

 See Revised Code of Washington, Title 51.28.050 – ‘Time limit for filing application or enforcing claim for injury’ 

http://apps.leg.wa.gov/RCW/default.aspx?cite=51.28.050 

6

 See Revised Code of Washington, Title 51.28.055 – ‘Time limitation for filing claim for occupational disease ‘

http://apps.leg.wa.gov/RCW/default.aspx?cite=51.28.055 
6 

Washington Unemployment Insurance Data 

The Washington State Employment Security Department (ESD) collects and maintains 

unemployment insurance (UI) data on Washington employers subject to UI coverage. Employers are 

assigned an account, which may be divided into individual locations or ‘units’ designated by a reporting 

unit number. UI data contains physical location address data for reporting units. 

Employers are required to file employment and wage information for their UI account with ESD. For 

each active UI account, employers submit quarterly reports that include the name, social security 

number, total hours worked, and wages paid for each individual employed that quarter. Note that 

worker data are reported at the level of the UI account and not the more granular reporting unit. ESD 

also assigns industry codes based on the establishment’s primary economic activity. 

UI data bridges the SOII and WC data. UI data, submitted to BLS for the Quarterly Census of 

Employment and Wages, is used to populate the LDB which serves as the sample frame for SOII. UI data 

can be linked to WA WC data through the Washington State UBI number. WC claims among a SOII 

sampled workforce can be identified by linking WC claims data to UI data through worker names and 

social security numbers. 

Washington UI data are available to SHARP researchers through an agreement with ESD. 

Changes in data from 2000 – 2011:

Effective January 1, 2002, OSHA’s Recordkeeping Rule underwent significant revisions. Because BLS 

relies on the OSHA case definition to determine which workplace injuries and illnesses are SOII 

reportable, these revisions to the OSHA recordkeeping regulations changed the types of cases required 

to be reported in SOII. Thus, data recorded prior to 2002 is considered not readily comparable to data 

recorded under the new rules and constitutes a break in SOII injury and illness data. Relevant WC 

regulations remained unchanged from 2000 through 2011, however, changes in the OSHA 

recordkeeping rules impact the comparability of SOII data with WC claims data. 

Specific changes to the rule impacting recordability criteria for determining DAFW cases and 

inclusion in the SOII case and demographic file or comparability to WC claims are: 

 Counting calendar days instead of workdays 

{The OSHA counting convention adopted as part of the 2002 changes is more closely aligned with 

WA WC guidelines for measuring duration of missed work – as of 2002, both use calendar days 

to count missed work. Prior to the 2002 changes, it is possible that an injury eligible for wage 

replacement in WC would not meet the OSHA recordable case criteria, and thus not included in 

the SOII case and demographic data, because time loss occurred when the worker was not 

scheduled to work. However, given the three-day waiting period for time loss eligibility in WA, 

prior to 2002, the worker would need to have been off the schedule for more than three days to 

be eligible for wage replacement yet not classifiable as DAFW; simply missing work over the 

weekend would not be sufficient to be eligible for wage replacement payments.} 

 Requiring a significant degree of aggravation for a preexisting injury or illness to be considered 

work-related 

{Prior to 2002, any new event or exposure was considered a new OSHA recordable case. WA WC 

defines aggravation as “a worsening of a once-fixed and stable occupational injury or disease 

that leads to temporary or permanent increase in disability”. When the preexisting injury or 

illness is work-related, a closed claim will be opened provided there is proof of aggravation or 

worsening of the condition. But “the worsening cannot be due to an unrelated condition, natural 

progression, or a new injury.” When the preexisting injury or illness is not work-related, L&I will 

pay for medical treatment if the condition was worsened or aggravated by a work-related 

exposure or injury. The pre-2002 OSHA definition may lead to multiple exposure-based cases that 

link to a single claim from an earlier date. The 2002 OSHA definition narrows the criteria, 
7 

stipulating a “significant degree of aggravation” for the case to be recordable, and providing 

employers with justification for not recording a particular case. Again, the 2002 change may 

align the OSHA definition more closely to the WA WC practices.} 

 Extending exceptions to the definition of work-relatedness to cases involving the eating and 

drinking of food and beverages, common colds and flu, blood donations, exercise programs, 

mental illness 

{Similar to the OSHA recordkeeping changes adopted in 2002, mental illness caused by stress, 

common colds and flu, and voluntary blood donations are not covered by WA WC. WC coverage 

also does not extend to: participation in social activities, recreational or athletic activities, event 

or competitions, and parties or picnics unless participation occurs during work hours, the 

employer paid the worker to participate, or the employee was ordered or perceived to be 

ordered to participate by the employer. Again, the 2002 change may align the OSHA definition 

more closely to the WA WC practices.} 

 Excluding motor vehicle accidents occurring on a company parking lot or company access road 

while the employee is commuting to or from work 

{Parking lot injuries are viewed similarly in WA WC, excluding from coverage “parking areas” and 

time spent going to or coming from the employer’s place of business (however, coverage 

includes time spent going to and from work on the jobsite).} 

 Requiring employers to establish procedure for employees to report injuries and illnesses 

{Establishing an employee reporting system may increase the number of cases recorded on the 

OSHA log in two ways: 1. employee reporting would increase the number of injuries made known 

to recordkeepers that, prior to implementation of such a system, recordkeepers would not have 

known about, or 2. recordkeepers may have had knowledge of all injuries and illnesses, if only 

through notification from L&I after a worker had filed a claim, but recorded on the OSHA log only 

injuries reported internally. Increasing internal reports of injuries may have increased the 

number of cases meeting a recordkeeper’s [erroneous] case recording criteria.}

 Enhancing employee privacy 

{The 2002 OSHA rules prohibit employers from recording the names of workers on the 300 log for 

certain types of injuries and illnesses. Complicating the attempt to match SOII cases lacking 

worker names to WC claims, this may result in more unmatched injuries. However, we 

encountered this issue in the 2006 – 2008 data match and were able to identify matches using 

other data elements.} 

Several other OSHA recordkeeping changes were effective January 1, 2002. It is unclear to what 

degree, if any, they impact SOII inclusion and/or comparability to WC claims. These include: 

 Introducing new forms to the replace the OSHA No. 200 form: the OSHA Form 300, Log of WorkRelated Injuries and Illnesses; OSHA Form 300A, Summary of Work-Related Injuries and 

Illnesses; and the OSHA Form 301, Injury and Illness Incident Report. 

 Clarifying recordable injuries and illnesses as those resulting in: death, days away from work, 

restricted work or transfer to another job, medical treatment beyond first aid, loss of 

consciousness, or diagnosis of a significant injury or illness by a physician or other licensed 

health care professional. 

 Requiring the same recording criteria (listed in previous bullet point) of both injuries and 

illnesses whereas prior to 2002, all illnesses were recordable. 

 Including new definitions of medical treatment, first aid, and restricted work. 

 Clarifying the recording of “light duty” or restricted work cases as restricted from “routine job 

functions”, defined as work activities the employee regularly performs at least once weekly.
8 

 Requiring the recording of all needlestick and sharps injuries involving contamination by another 

person’s blood or other potentially infectious material. 

 Allowing employee access to individual 301 forms. 

 Requiring certification of summary (300A form) by company executive. 

Changes to OSHA recordable case criteria are necessarily reflected in SOII data, dictating which 

injuries and illnesses are to be included in or excluded from the survey. There were additional changes in 

SOII data that were unlikely to impact case reporting or matching to WC claims but do affect the 

comparability of data over time, namely changes in the injury classification and industry coding systems 

that were adopted between 2000 and 2011 (see figure below). 

Record Linkage 

Establishments excluded from the study 

Not all establishments that participated in SOII were included in the linkage study. Establishments 

were excluded for one of three reasons: establishments were present in the SOII file but without UI 

account information; establishments with SOII-provided UI account information could not be found 

within the WA UI data; and establishments were not covered by the WA Industrial Insurance (i.e., WC) 

system. Railroad and mining establishments are not sampled from the LDB and their UI account 

information is not recorded in SOII data. Industry classifications, available in UI as either SIC codes (for 

all years) or NAICS codes (for years 2002 – 2011) were used to identify the water transportation, ship 

and boat building, seafood product preparation and packaging, and fishing establishments that have 

workers’ compensation covered through either the Longshore and Harbor Workers Compensation Act or 

the Jones Act. The ownership code in UI was used to identify establishments owned by tribes – as 

sovereign tribes they are not required to participate in Washington’s Industrial Insurance system. 

Identifying BLS participants in Washington workers’ compensation data 

Using the UI account and reporting unit numbers provided in the SOII establishment file, BLS 

sampled establishments were identified within Washington’s UI data from the quarter when the sample 

Changes in SOII data, 2000 - 2011

Changes in injury data

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Changes in industry data

Change in OSHA 

recordkeeping regs: 

break in SOII injury 

data

Change in injury 

classifications 

(OIICS1992/2007→ 

OIICS 2.0) : break in 

SOII injury data

Change in industry 

classification 

(NAICS 2002→ 

NAICS 2007): no 

break in SOII 

industry data

Change in industry 

classification 

(SIC→NAICS 2002): 

break in SOII industry 

data
9 

was drawn, i.e., seven quarters prior to the beginning of the survey year. The sampled establishments 

were mapped through successive quarters within the UI data to identify changes in ownership, physical 

location, or a break in liability (e.g., a quarter in which there was no employment reported). 

Next, we identified individuals employed by SOII respondents during the survey year using the UI 

account information current at the time of the survey. Worker identifiers for individuals reported in at 

least one of the four quarters of the survey year among SOII-participating UI accounts were extracted 

from the Washington UI database. These SOII-participating UI accounts were either a. sampled in their 

entirety or b. limited to a reporting unit. When a SOII establishment represented a report unit, rather 

than the entire UI account, the workforce identified from the UI account data was greater than the 

workforce sampled, since workers are reported at the UI account level. Establishment characteristics 

were used later in the record linkage process to limit workers to those employed at the sampled 

reporting unit. A discussion of this process occurs later in this section (see section titled Identification of 

WC claims that meet SOII case criteria) 

Using the social security numbers reported in UI data among SOII-participating UI accounts to 

identify the surveyed workforce, we extracted WC claims among the sampled workforce with an injury 

date in the survey year in which the establishment participated. All workers’ compensation claims for 

individuals with identified SSN were extracted regardless of claim liability status, meaning rejected 

claims, claims for medical-aid only, and indemnity claims were extracted for linking to SOII cases. 

Linking BLS cases and Washington workers compensation claims data 

Record linkage to WC claims was attempted for all cases reported in SOII by included 

establishments. To allow for differences between SOII and WC in the characterization of missed work, 

no restrictions were made to the WC claim population prior to linking. This approach identified more 

claims than are likely eligible for reporting in SOII (similar to extracting all claims for an entire UI account 

when SOII participation was limited to a reporting unit). Record level exclusions were applied after the 

linkage process was complete. 

Research staff developed SAS code to deterministically link records through an iterative process, 

altering the linking criteria of one or more variables in each successive attempt. SOII cases linked to WC 

claims based on the following data elements: worker first name, last name, date of birth or age at injury, 

and date of injury. First and last names were allowed to match identically or phonetically; on later 

attempts, first name was also allowed to match on first initial or not at all. Over the course of the 

multiple record linkage attempts, the matching requirement for date of birth was broadened iteratively 

from exact match between SOII and WC to within 7 days, 31 days, 65 days, 365 days, 3,660 days, and 

finally 7,220 days. For cases where date of birth was not provided, the age at injury was allowed to vary 

from exact, to within 1 year, then within 10 years. After each iteration, potential links were manually 

reviewed by research staff to confirm that the new criteria identified true matches. 

Linking iterations followed a hierarchy so that links to the more relevant claims preceded other 

attempts. Links to claims with wage replacement were attempted prior to links among medical only 

claims, with all other variables being equal. Linkages were first attempted among the SOII cases in the 

‘final cases’ file and then followed by an attempt to link cases in the ‘unusable case’ file. Once linked, 

both cases and claims were removed from the group of records available for subsequent linkage 

attempts. 

Record linkage procedures resulted in three groups of records: linked SOII-WC cases, unlinked SOII 

cases, and unlinked WC claims. As noted above, more WC claims were extracted than were expected to 

meet the SOII case reporting criteria because they were either a. employed by the sampled employer 

some location other than the sampled reporting unit or b. filed for an injury that did not result in missed 

work (e.g. rejected claims). This necessitated reducing claims to those eligible for SOII as a DAFW case. 
10

Claims among workers employed at a location other than the sampled unit were identified using 

employer and establishment identifiers. When the sampled establishment represented one of many 

reporting units within a UI account, unlinked claims were removed based on discordance between UI 

and WC data on: employer UBI; employer city, and employer street. When the UBI, city, or street of the 

WC business location associated with the unlinked WC claim differed from the UBI, city, or address of 

the physical location data for the sampled reporting unit or from the reporting unit associated with the 

majority of linked SOII-WC cases, the unlinked claim was considered to be associated with a reporting 

unit other than the sampled unit. These claims were excluded from the group of unlinked claims and 

considered not reportable to SOII. For sampled establishments that represented the entirety of a UI 

account (defined as a reporting unit=’00000’ and a reporting unit description=’All WA State Employees’), 

all claims were retained since these workers were reported in UI data as working for the sampled UI 

account. 

Workers with multiple employers in the quarter of injury required an additional step to link the 

unmatched claim to the appropriate employer. Identifying workers from the UI data among sampled 

employers established a link between the worker and the sampled employer, but not necessarily 

between the claim and the sampled employer. For workers with multiple employers, the unmatched 

claim may have been assigned in WC to a SOII establishment or to an employer not participating in SOII. 

To link the unmatched claims to the sampled establishment, claims were retained when the claim UBI 

matched the establishment UBI, or, in the case of non-matching UBI, when the name of the company 

assigned the claim in WC was more similar to the name of the SOII-sampled company than the name of 

the worker’s additional employer(s) as documented in UI. 

To identify claims for injuries that resulted in one or more days of missed work (thus meeting the 

SOII DAFW case criteria), we used WC indemnity payment information. State funded claims that 

received payments for missed work, or self-insured claims classified as eligible for time loss payments7

were considered to have met the missed work criterion to be recordable as a DAFW case. Claims limited 

to payments for medical-aid only, rejected claims, and claims classified as eligible for some other 

indemnity payment (such as loss of earning power, kept on salary) lack conclusive evidence of missed 

work and were therefore removed from the pool of unlinked claims. Once we limited unlinked claims to 

injuries resulting in missed work, we used claim event dates to indicate whether the missed work 

occurred within the survey year. When the WC date for first medical treatment, claim establishment, 

disability, or initial time loss payment occurred after the survey year, records (both linked and unlinked 

WC claims) were excluded from further analyses. Although these injuries occurred during the survey 

year and eventually resulted in missed work, the claim data suggested the missed work did not occur 

until after the survey year concluded and thus, would not have been recordable as a DAFW case during 

the survey year. 

We used the WC injury date to remove unlinked claims outside of the BLS subsample instructions. 

For establishments asked to report on a subsample of cases based on the injury date (e.g. injuries that 

occurred in the first three months of the year, or injuries that occurred on the 15th day of the month), 

any unlinked claim with an injury date outside the subsample timeframe was removed from the group 

of unlinked claims. 

All records in the BLS ‘unusable’ case file – both linked and unlinked – were excluded from analyses. 

Linking claims to cases reported in the ‘unusable’ file identifies claims that may otherwise have been 

considered unlinked or unreported. 

The linking procedures allowed for a WC claim to be associated with more than one sampled 

establishment. This occurred when a claimant worked for a UI account with multiple sampled reporting 

 

7

 No lost time payment information, such as total days missed or total amount awarded for missed work, is 

captured for self-insured claims, only their status as eligible for time loss payments. 
11

units and few differences among the units’ physical location data. When available, the accident city 

documented in the WC claim data as used to link the claim to the appropriate reporting unit. If the WC 

accident city was a location other than the physical location city of the sampled report unit, the claim 

was considered outside the scope of the sampled workforce and excluded from the analysis. In some 

cases, the data available were insufficient to assign a claim to a single reporting unit. Whenever 

possible, distinct claims were analyzed to avoid “double counting” unlinked claims. For example, a 

single claim associated with three grocery store establishments located in the same city would be 

considered as one unlinked claim and not three. 

SOII case weights were applied to both linked and unlinked WC claims. Unlinked claims were 

assigned the case weight associated with the establishment determined to be responsible for reporting 

the claim. When an unlinked WC claim was associated with more than one sampled establishment, the 

weights were averaged into one case weight. 

Analysis 

Reporting patterns over the twelve year period are described by industry, injury type, and event or 

exposure leading to injury or illness. Generalized linear models were used to estimate the change in 

underreporting over time. Logistic regression models were used to test the association between the 

survey year and underreporting, as well as between establishment or case characteristics and the 

probability of a claim being unreported. 

Establishments were grouped into the following 14 categories based on the SIC codes assigned in UI 

data: 

Industry description SIC codes

Agriculture, Forestry, and Fishing 0

Construction 15-17

Manufacturing 2-3

Transportation 40-47

Communications, Electric, Gas, Sanitary Services 48-49

Wholesale Trade 50-51

Retail Trade 52-59

Finance, Insurance, and Real Estate 60-67

Health Services 80

Educational Services 82

Social Services 83

Services other than hlth, ed, soc 70-79, 81, 84-89

Public Administration 9

Unclassified blank

We used to following event or exposure and nature of injury groupings to assess reporting 

trends in injury characteristics. OIICS division groupings were used to assess event or exposure. 

Nature of injury or illness codes were grouped based on frequency rankings, following the 

hierarchical structure of the OIICS system. The Washington State Dept. of Labor and Industries 

developed a crosswalk between the ANSI and OIICS codes, allowing us to use OIICS (2007) codes for 

the full ten years of the study period. 
12

Event or exposure description 2007 OIICS code

Assaults and violent acts 6

Bodily reaction and exertion 2

Contact with objects and equipment 0

Exposure to harmful substance or environment 3

Falls 1

Fires and explosions 5

Other events or exposures 9

Transportation accidents 4

Nonclassifiable 9999

Nature of injury description 2007 OIICS codes

Sprains, strains, tears 021

Fractures 012

Bruises, contusions 043

Multiple traumatic injuries and disorders 08*

Nonspecified injuries and disorder 097*

All other traumatic injuries All other 0* codes

Nontraumatic/nonacute injuries 1*, 2*, 3*, 4*, 5*, 8*

Nonclassifiable + Missing 9999, Blank

The research study was approved by the Washington State Institutional Review Board. 
13

RESULTS 

Linkage Results 

Of the 58,835 establishment records from 2000 – 2011 Washington SOII data, 5,382 establishments 

(7.3%) were excluded because they: lacked UI identifiers in SOII data (4,279 railroad and mining 

establishments not sampled by BLS); were not identified in WA UI data using SOII UI identifiers (28 

establishments); or were not covered under the WA WC system (1,075 establishments identified 

through industry classification codes or UI ownership codes). A total of 53,453 establishment records 

over twelve years of survey data were included in the record linkage study; the percent included ranged 

from 89.8% in 2006 to 91.8% in 2011. See Figure 1 for percent of SOII establishments meeting the 

exclusion criteria by year. 

Case reports among included establishments totaled 94,123. After executing the linking algorithm, 

91,678 cases (97.4%) matched a WA WC claim. 

Limiting records (linked cases and unlinked claims) to those with WC evidence of work absence in 

the survey year, and removing rejected claims, claims for medical-aid only which may have resulted in 0 

or up to three days of missed work, indemnity claims awarded for something other than missed work, 

and lost time claims for work absence that first occurred after the survey year brought the total number 

of records to 47,985 linked records and 23,759 unlinked WC claims. Annual SOII-eligible WC claims 

ranged from 5,011 records in 2001 to 7,762 records in 2006 (See Figure 2). 

Figure 1. SOII-participating WA establishments by inclusion, exclusion criteria for linking to WA WC data, 

2000 - 2011 

91.3% 91.1% 91.1% 90.9% 90.9% 90.6% 89.8% 90.0% 90.3% 91.0% 91.4% 91.8%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2000

n=4853

2001

n=4678

2002

n=4670

2003

n=4869

2004

n=4569

2005

n=4700

2006

n=5076

2007

n=5069

2008

n=5075

2009

n=5088

2010

n=5035

2011

n=5153

Excluded: UI identifiers not provided in SOII

Excluded: Not found in WA UI data using SOII UI indentifiers

Excluded: Not covered under WA WC

Included: SOII establishments linked to WA UI data
14

Figure 2. Number of SOII-eligible WA WC time loss claims by year and record 

linkage results. 

Trends in Reporting 

 Among SOII-eligible WC claims, the percent of unlinked (or unreported) claims increased over time, 

from a low of 29.7% of SOII eligible claims in 2001 to a high of 38.9% in 2010 (Figure 3). In the years 

following the 2002 OSHA recordkeeping regulation changes, the least amount of unlinked claims 

occurred in 2006, with 30.6% of SOII-eligible claims not linked to a SOII case. The largest year-to-year 

increase in unreported claims occurred between 2008 and 2009, when the percent of total claims 

unreported increased 3.0%. Over the ten year period, underreporting increased each year by an 

estimated 0.8% (p<.0001). However, there were two distinct patterns: between 2002 and 2006, 

underreporting decreased slightly (0.4% per year, p=0.02), and between 2007 and 2011, underreporting 

increased by an estimated 2.1% (p<.0001). 

Between 2002 -2011, approximately half of all unlinked claims were associated with UI accounts 

sampled in their entirety and half were associated with establishments sampled at a UI reporting unit. 

The greatest difference in the proportion was observed for 2009, where 58% of unlinked claims were 

associated with a sampled reporting unit, compared with 42% from sampled UI accounts (data not 

shown). 

For each survey year from 2002 through 2011, rates of underreporting were lower among sampled 

UI accounts compared with sampled reporting units (Figure 4). Among UI accounts sampled in their 

entirety, unreported claims made up as little as 24.1% of all SOII-eligible WC claims in 2003 and as much 

as 32.1% of all SOII-eligible WC claims in 2010. Among sampled reporting units, unlinked claims ranged 

from 38.1% of SOII-eligible claims in 2006 to 46.1% of SOII-eligible claims in 2010. On average, the 

percent of claims unlinked among sampled reporting units was 15% greater than the portion of unlinked 

claims among UI accounts. 

Between 2003 and 2011 among sampled UI accounts, the percent of unreported SOII-eligible claims 

either increased or experienced no change from the previous year. In the same time period, 

underreporting decreased among report units in 2006 and again in 2008. In general, the change in 

underreporting from one year to the next was usually greater among sampled report units than sampled 

UI accounts. For example, between 2008 and 2009, unreported claims increased from 40.6% to 45.3% 

 -

 1,000

 2,000

 3,000

 4,000

 5,000

 6,000

 7,000

 8,000

 9,000

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

UNLINK

LINK
15

among sampled report units and from 27.8% to 28.0% among sampled UI accounts. For sampled 

reporting units, the greatest one year increase in the percent of claims unreported was observed in

2009 (a 4.7% increase); for sampled UI accounts, the greatest one year increase occurred the following 

year in 2010 (a 4.1% increase). For both sample units, underreporting peaked at the end of the ten year 

study period (32.1% of SOII-eligible claims among sampled UI accounts in 2010 and 2011 and 46.1% 

among sampled reporting units in 2010).

Applying the SOII case weights to the SOII-eligible WC claims, both linked and unlinked, produced 

estimates of unreported claims that ranged from a low in 2007 of 28.9% to a high in 2002 of 42.8% 

(Figure 5). The pattern of underreporting for both claim counts and estimated injuries was similar, 

especially in years 2008 – 2011, where the patterns converged; both the magnitude of underreporting 

and the year over year trend in underreporting were similar for claim counts and weighted estimates. 

Using the survey weights to estimate the total number of time loss injuries, both reported and total 

injuries decreased between 2002 and 2011 (Figure 6). Note that based on the study case inclusion 

criteria, these injuries are defined as ‘injuries with work absence in the survey year and eligible for WC 

compensation for missed work’ and differ from the SOII DAFW case definition. Also, the figure presents 

total estimated numbers of injuries and not an injury rate. 

Trends in reporting by workers’ compensation insurer 

Self-insured claims made up a disproportionate share of unreported cases. Between 2002 and 2011, 

claims from self-insured employers averaged 57.7% of the total number of SOII-eligible claims among 

sampled establishments and 65.0% of all unreported claims. Claims among state funded employers 

averaged 42.3% of total claims and 35.0% of unreported claims. In each year, the rate of unreported 

self-insured claims exceeded the rate of unreported state funded claims (Figure 7), with the greatest 

difference observed in 2010 (45.2% unreported self-insured claims compared with 28.2% unreported 

state funded claims). Underreporting increased among both groups, although the rate of change was 

greater among self-insured claims (annual increase of 2.0% among self-insured claims compared with 

0.4% among state funded claims, 2006 – 2011). 

Distinguishing between workers’ compensation insurer and sampled unit, claims among self-insured 

establishments sampled as a reporting unit had the highest rates of underreporting (Figure 8). Between 

2006 and 2009, underreporting was similar for state funded UI account, self-insured UI accounts, and 

state funded sampled reporting units. The greatest overall increase in underreporting was observed 

among self-insured UI accounts (annual increase of 1.5%) and the lowest among state funded UI 

accounts and self-insured reporting units (an annual increase of 0.1% for each). 
16

Figure 3. Percent of SOII eligible WA WC time loss claims by record linkage result, 

2000 – 2011. 

Figure 4. Annual percent of SOII-eligible WA WC time loss claims unlinked among 

sampled unit, 2002 – 2011. 

67% 69% 68% 69% 69% 67% 67% 64% 61% 62%

33% 31% 32% 31% 31% 33% 33% 36% 39% 38%

70% 70%

30% 30%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Linked claims(reported)

Unlinked claims (unreported)

43.6% 40.8% 42.3% 43.3%

38.1%

42.1% 40.6%

45.3% 46.1% 44.6%

26.9% 24.1% 24.4% 24.4% 25.7% 27.7% 27.8% 28.0%

32.1% 32.1%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Percent of SOII-eligible claims unlinked among sampled report units

Percent of SOII-eligible claims unlinked among sampled UI accounts
17

Figure 5. Annual percent of SOII eligible WA WC time loss claims unlinked, based 

on unweighted case counts and weighted estimates, 2002 – 2011. 

Figure 6. Total estimated SOII-eligible WA WC time loss injuries based on SOII case 

weights, by report status, 2002 – 2011. 

 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Unreported claims, weighted estimate (ave)

Unlinked claims, unweighted

 -

 5,000

 10,000

 15,000

 20,000

 25,000

 30,000

 35,000

 40,000

 45,000

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Unreported claims

Reported claims
18

Figure 7. Annual percent of SOII-eligible workers’ compensation time loss claims 

unlinked among establishments self-insured for workers’ compensation 

insurance and establishments insured through the Washington State Fund, 

Washington, 2002 – 2011. 

Figure 8. Annual percent of SOII-eligible WA WC time loss claims unlinked among 

sampled unit and workers’ compensation insurer, 2002 – 2011. 

39.0%

34.4% 34.6% 32.7% 33.5%

38.8% 38.0% 40.5%

45.2% 43.2%

24.8% 25.8% 27.9% 29.7% 27.0% 27.3% 26.9% 29.7% 28.2% 28.7%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Self-insured

State Fund

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Self-insured, Report unit Self-insured, UI account

State Fund, Report unit State Fund, UI account
19

Trends in reporting by establishment size 

Adopting the five size categories used by BLS, on average the smallest establishments accounted for 

1% of the unlinked claims and 15% of the weighted estimate of unreported claims between years 2002 

through 2011. The largest two size classes (establishments with 250 or more employees) accounted for 

more than 60% of all unreported claims (claim counts) but just over 20% of the weighted estimate of 

unreported claims (Table 1). 

The rate of underreporting differed by establishment size (Table 2). Compared to establishments 

with 1,000 or more employees, claims among smaller establishments (1 – 49 employees), were more 

likely to be unreported and claims among establishments with 50-249 employees were less likely to go 

unreported. 

Between 2002 and 2006, controlling for size class, the rate of underreporting did not change over 

the five year span (p=0.3). Between 2006 and 2011, underreporting increased in each of the five size 

classes (Figure 9). The greatest increase in underreporting during that time period occurred among 

establishments with 11-49 employees (an annual increase of 2.9%), followed by establishments with 

1,000 or more employees (annual increase of 2.6%, 2006 - 2011). Underreporting fluctuated greatest 

among establishments with 10 or fewer employees; however between 2003 and 2011, these rates were 

based on fewer than 100 total claims annually. 

Table 1. Unlinked SOII-eligible WA WC claims by establishment size. 

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Mean, 

2002-2011

Unweighted claim counts

1-10 employees 4% 1% 1% 3% 2% 1% 2% 1% 1% 1% 1%

11-49 employees 9% 10% 9% 8% 7% 13% 8% 10% 13% 6% 9%

50-249 employees 27% 27% 32% 26% 32% 31% 31% 31% 24% 28% 29%

250-999 employees 23% 29% 26% 24% 30% 32% 36% 36% 35% 34% 31%

1000+ employees 37% 33% 32% 40% 29% 24% 23% 22% 28% 31% 30%

Total unlinked claims 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100%

Weighted estimate of unreported claims

1-10 employees 45% 9% 5% 21% 13% 6% 15% 11% 7% 16% 15%

11-49 employees 17% 35% 30% 25% 31% 42% 28% 37% 40% 27% 31%

50-249 employees 24% 34% 43% 32% 36% 32% 35% 32% 26% 31% 33%

250-999 employees 10% 14% 15% 14% 12% 13% 15% 14% 16% 15% 14%

1000+ employees 5% 8% 7% 8% 9% 6% 6% 6% 10% 10% 7%

Total unlinked claims 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100%

Table 2. Probability of unlinked WA WC claims by survey year and establishment size, 2002 – 2011. 

Odds ratio 95% CI

Survey year 1.04 1.04 1.05

Establishment size 

1-10 employees 1.24 1.09 1.42

11-49 employees 1.17 1.10 1.24

50-249 employees 0.89 0.86 0.93

250-999 employees 1.02 0.98 1.06

1000+ employees Referent
20

Figure 9. Annual percent of SOII eligible WA WC time loss claims unlinked, based on unweighted case 

counts and weighted estimates, by establishment size, 2002 – 2011. 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

1-10 Employees

unweighted count of unlinked claims

weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

11-49 Employees

unweighted count of unlinked claims

weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

50-249 Employees

unweighted count of unlinked claims

weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

250-999 Employees

unweighted count of unlinked claims

weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

1,000+ Employees

unweighted count of unlinked claims

weighted estimate of unreported claims
21

Trends in reporting by industry 

Between 2002 and 2011, claims among establishments partially exempt from OSHA recordkeeping 

requirements based on SIC codes (not number of workers) averaged 8% of the annual total number of 

SOII-eligible WC claims, and 8% of the annual number of unreported claims. Little difference was 

observed between the annual rates of underreporting among establishments required to maintain OSHA 

injury and illness records and the rates among establishments partially exempt from recordkeeping 

(Figure 10). The greatest difference in rates was seen in 2011 where underreporting among partially 

exempt establishments was 5% higher than the rate among non-exempt establishments. 

Figure 10. Annual percent of SOII-eligible workers’ compensation time loss claims 

unreported among establishments required to maintain annual OSHA injury and 

illness records and establishments required to maintain recorded only when 

instructed by BLS or OSHA (known as partially exempt), Washington, 2002 –

2011. Exemption status based on SIC codes listed in WA State statute and not 

number of employees. 

35.9%

30.1%

34.0% 32.7% 33.9% 34.3% 33.6% 36.6%

40.8% 43.2%

33.1% 31.1% 31.9% 31.7% 30.6% 33.6% 33.1% 36.2% 39.2% 38.2%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Partially exempt (claim count)

Required (claim count)
22

Establishments were grouped into one of fourteen industry categories based on the SIC code 

assigned in the UI data. Between 2002 and 2011, the three industries contributing the greatest number 

of unlinked claims to the total unweighted claim count were: Manufacturing (16%); Retail Trade (15%); 

and Health Services (12%) (Table 3). Based on the weighted estimate, the greatest percent of 

unreported claims came from Retail Trade (22%), Transportation (13%), and Manufacturing (10%). 

Table 3. SOII-eligible WA WC claims unlinked by industry and year. 

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Mean, 

2002-

2011

Unweighted claim counts

Agriculture, Forestry, and Fishing 2% 2% 4% 2% 2% 3% 3% 5% 3% 3% 3%

Construction 5% 4% 5% 4% 5% 9% 9% 5% 3% 3% 5%

Manufacturing 21% 21% 16% 15% 17% 19% 18% 11% 7% 9% 16%

Transportation 7% 5% 9% 5% 8% 8% 8% 7% 6% 15% 8%

Communications, Electric, Gas, Sanitary 12% 15% 10% 12% 9% 16% 7% 6% 13% 5% 11%

Wholesale Trade 4% 5% 5% 6% 4% 4% 3% 5% 3% 3% 4%

Retail Trade 12% 16% 13% 14% 17% 15% 11% 17% 16% 15% 15%

Finance, Insurance, and Real Estate 1% 1% 1% 2% 1% 1% 0% 0% 0% 0% 1%

Services other than hlth, ed, soc 10% 7% 9% 9% 7% 6% 7% 7% 7% 6% 7%

Health Services 12% 10% 8% 7% 11% 9% 12% 14% 17% 20% 12%

Educational Services 7% 6% 8% 9% 5% 5% 16% 17% 13% 13% 10%

Social Services 1% 1% 2% 3% 2% 2% 2% 2% 3% 3% 2%

Public Administration 5% 6% 6% 9% 10% 2% 3% 3% 9% 6% 6%

Unclassified 0% 0% 5% 2% 1% 2% 1% 0% 0% 0% 1%

Total unlinked claims (counts) 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100%

Weighted estimate of unreported claims

Agriculture, Forestry, and Fishing 2% 4% 3% 2% 4% 3% 2% 5% 3% 2% 4%

Construction 5% 6% 10% 12% 11% 10% 12% 12% 5% 4% 8%

Manufacturing 8% 12% 10% 10% 11% 10% 15% 10% 6% 9% 9%

Transportation 44% 7% 19% 7% 8% 10% 13% 8% 7% 8% 10%

Communications, Electric, Gas, Sanitary 2% 4% 3% 10% 6% 7% 3% 12% 21% 3% 6%

Wholesale Trade 2% 7% 8% 6% 6% 5% 4% 6% 2% 13% 5%

Retail Trade 16% 31% 23% 25% 20% 22% 16% 21% 19% 25% 21%

Finance, Insurance, and Real Estate 1% 5% 1% 2% 3% 2% 1% 0% 1% 1% 2%

Services other than hlth, ed, soc 7% 6% 9% 11% 10% 13% 11% 7% 11% 9% 11%

Health Services 5% 6% 4% 5% 10% 7% 7% 8% 11% 10% 8%

Educational Services 2% 2% 2% 5% 2% 2% 6% 4% 5% 8% 3%

Social Services 2% 1% 5% 1% 3% 6% 3% 4% 2% 3% 3%

Public Administration 3% 8% 2% 4% 7% 3% 6% 3% 6% 5% 8%

Unclassified 0% 0% 2% 0% 1% 2% 2% 0% 0% 0% 1%

Total unlinked claims (weighted est) 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100%
23

Rates of underreporting varied by industry and by year (Table 4). Compared to Manufacturing, 

underreporting was less likely in Finance, Insurance, and Real Estate. The likelihood of unreported 

claims was similar in Manufacturing, Social Services, Educational Services, Agriculture Forestry Fishing, 

Wholesale Trade, and Public Administration. Compared to Manufacturing, underreporting was greater 

in Health Services, Construction, Retail Trade, Transportation, and Other Services, and greatest among 

establishments in Communications, electric, gas, sanitary services, where the odds of underreporting 

were more than five times the odds of underreporting in Manufacturing. 

The greatest increase in underreporting was observed among Educational Services (from a low of 

15% in 2003 to a high of 47% in 2009), Transportation (from a low of 27% in 2003 to a high of 56% in 

2011), and Health Services (from a low of 21% in 2004 to a high of 46% in 2011) (Figure 11-a). For 

establishments in Wholesale Trade, Manufacturing, and Agriculture, Forestry, and Fishing the rate of 

underreporting did not change over the ten year period. Underreporting in Retail Trade decreased by 

an estimated 0.6% each year over the ten year period (p<.01). Between 2002 and 2011, the annual 

average number of unreported claims was less than one in three SOII-eligible claims in each of the 

fourteen industries except: Communications, Gas, Electric, and Sanitary Services (annual average of 70% 

of SOII-eligible claims unreported); Other Services (annual average of 41% of SOII-eligible claims 

unreported); Retail Trade (annual average of 37% of SOII-eligible claims unreported); and Transportation 

(annual average of 35% of SOII-eligible claims unreported). 

Figure 11-b presents the difference in reporting trends by industry for all establishments compared 

with those sampled at the UI account. The greatest impact is seen in Educational Services, where no 

increase in underreporting is observed among the Educational establishments sampled at the level of 

the UI account. There is also a large difference between sample units in Communications, Electric, Gas, 

and Sanitary Services, but the trend for sampled UI accounts is similar to that for all establishments in 

the industry grouping. 

Table 4. Probability of unlinked WA WC claims by survey year and industry, 2002 – 2011. 

OR 95% CI

Survey year 1.05 1.04 1.05

INDUSTRY (SIC)

Manufacturing Referent

Finance, Insurance, and Real Estate 0.81 0.68 0.97

Unclassified 0.92 0.79 1.07

Social services 0.95 0.85 1.07

Educational services 0.99 0.93 1.06

Agriculture, Forestry, and Fishing 1.01 0.91 1.12

Wholesale trade 1.03 0.94 1.13

Public administration 1.05 0.97 1.14

Health services 1.11 1.04 1.18

Construction 1.17 1.08 1.28

Retail trade 1.24 1.17 1.32

Transportation 1.27 1.19 1.37

Services other than hlth, ed, soc 1.57 1.45 1.69

Communications, electric, gas, sanitary 5.67 5.20 6.19
24

 Figure 11-a. SOII-eligible Workers’ Compensation time loss claims by industry, Washington 2002 – 2011.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Educational Services

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Health Services

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Transportation

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Social Services

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Construction

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Other Services

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Communications, Electric, Gas, Sanitary Services

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Public Administration

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Wholesale Trade

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Manufacturing

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Agriculture, Forestry, Fishing

Unweighted count of unlinked claims

Weighted estimate of unreported claims

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Retail Trade

Unweighted count of unlinked claims

Weighted estimate of unreported claims
25

Figure 11-b. SOII-eligible Workers’ Compensation time loss claims by industry among all establishments and those sampled at UI account, Washington 2002 – 2011. 

 

 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Educational Services

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Health Services

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Transportation

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled...

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Social Services

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Construction

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Services (other than hlth, ed, soc)

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Communications, Electric, Gas, Sanitary Services

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Public Administration

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Wholesale Trade

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Manufacturing

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Agriculture, Forestry, Fishing

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Retail Trade

Unweighted count of unlinked claims, all

Unweighted count of unlinked claims, sampled at UI account
26

Trends in reporting by injury characteristics 

Event or exposure leading to the injury 

Eighty-three percent of all SOII-eligible claims (linked and unlinked) resulted from one of three event 

or exposure divisions: bodily reaction or exertion (51.7%), contact with objects and equipment (15.9%), 

and falls (15.4%). The rate of underreporting was similar among injuries arising from contact with 

objects and equipment and injuries resulting from falls, and elevated among injuries from bodily 

reaction or exertion (Figure 12). Controlling for survey year, injuries from bodily reaction or exertion 

had a 31% increased odds of being underreported compared to injuries from falls and a 23% increased 

odds of underreporting compared to injuries from contact with objects and equipment (Table 5). The 

rate of underreporting of injuries from bodily reaction or exertion was estimated to increase each year 

by 0.9% (p<.0001), of injuries from contact with objects and equipment by 0.8% (p<.0001), and remain 

constant among injuries from falls. 

The remaining 15% of claims resulted from one of five events or exposures: transportation accidents 

(2.8%); assaults and violent acts (1.8%); exposure to harmful substances or environments (1.6%); fires 

and explosions (0.1%); and other events or exposures (8.3%). An additional 2.3% of claims were missing 

an event or exposure code. Injuries from exposure to harmful substances or environments, assaults and 

violent acts, and transportation accidents experienced an increase in unreported claims of 

approximately 20%, from their lowest rate of unreported claims to their highest during the ten year time 

period (Figure 13). 

Table 5. Probability of unlinked WA WC claims by survey year and event or exposure, 2002-11. 

OR 95% CI

Survey year 1.04 1.03 1.04

EVENT OR EXPOSURE

Bodily reaction and exertion Referent

Falls 0.76 0.73 0.80

Fires and explosions 0.77 0.40 1.46

Assaults and violent acts 0.80 0.70 0.91

Contact with objects and equipment 0.81 0.77 0.85

Exposure to harmful substances or environments 0.84 0.73 0.96

Transportation accidents 1.01 0.91 1.11

Other events or exposures 1.26 1.18 1.33

Figure 14 presents reporting trends for the three most common events within the six industries with 

the greatest numbers of estimated injuries (based on linked and unlinked claims). More than two out of 

three estimated injuries were among Construction, Manufacturing, Transportation, Retail Trade, Health 

Services, and Services other than health, education, or social services. 

Within Construction, the rate of unreported injuries from bodily reaction and exertion was greater 

in almost every year than the rate among injuries from contact with objects and equipment and injuries 

from falls. The rate of unreported injuries from falls was the lowest of the three events in almost every 

year. Higher rates of unreported injuries from bodily reaction and exertion were also observed within 

Manufacturing, although the difference between the rates for each event or exposure was not as great 

as seen in Construction. Few differences among the three events were observed for the other four 

industries. All three events appear to decrease between 2002 and 2011 within Retail Trade, and 

increase within Health Services. 
27

Figure 12. SOII-eligible WA WC time loss claims by select event or exposure 

resulting in injury or illness: contact with objects and equipment, falls, bodily 

reaction and exertion, 2002 – 2011. 

Figure 13. SOII-eligible WA WC time loss claims by select event or exposure 

resulting in injury or illness: exposure to harmful substances or environments, 

transportation accidents, assaults and violent acts, and other events or 

exposures, 2002 – 2011. 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Unlinked claims from bodily reaction and exertion

Unlinked claims from contact with objects and equipment

Unlinked claims from falls

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Unlinked claims from exposure to harmful substances or environments

Unlinked claims from assaults and violent acts

Unlinked claims from other events or exposures

Unlinked claims from transportation accidents
28

Figure 14. SOII-eligible WA WC time loss claims for select industries by three most common events or exposures, 2002 – 2011

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Construction

Bodily reaction and exertion

Contact with objects and equipment

Falls

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Manufacturing

Bodily reaction and exertion

Contact with objects and equipment

Falls

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Transportation

Bodily reaction and exertion

Contact with objects and equipment

Falls

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Retail Trade

Bodily reaction and exertion

Contact with objects and equipment

Falls

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Health Services

Bodily reaction and exertion

Contact with objects and equipment

Falls

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Other Services

Bodily reaction and exertion

Contact with objects and equipment

Falls
29

Nature of injury 

Controlling for survey year, underreporting varied by nature of injury. Fractures, Multiple traumatic 

injuries and disorders, Bruises, contusions, and Other traumatic injuries were more likely to be reported 

compared with Sprains, strains, tears (Table 6). Non-specified traumatic injuries, Non-traumatic 

diseases, conditions, disorders, and Non-classifiable conditions were less likely to be reported compared 

with Sprains, strains, tears. 

Between 2002 and 2011, underreporting increased among: Sprains, strains, tears; Non-specified 

traumatic injuries, Other traumatic injuries; Non-traumatic diseases, conditions, disorders; and Nonclassifiable condition. Marginally significant increases were observed among Multiple traumatic injuries 

and Fractures. Underreporting did not change in the same ten year time period for Bruises and 

contusions (Figure 15.)

Table 6. Probability of unlinked WA WC claims by survey year and nature of injury. 

OR 95% CI

Survey year 1.04 1.04 1.05

NATURE OF INJURY

Sprains, strains, tears Referent

Fractures 0.65 0.60 0.71

Multiple traumatic injuries and disorders 0.84 0.77 0.91

Other traumatic injuries 0.91 0.86 0.96

Bruises, contusions 0.91 0.84 0.99

Non-specified traumatic injuries and disorders 1.23 1.16 1.30

Non-traumatic diseases, conditions, disorders 1.28 1.20 1.36

Non-classifiable + missing 1.37 1.31 1.44
30

Figure 15. Annual percent of SOII eligible workers’ compensation time loss claims unreported among 

select nature of injury types or injury groups, Washington 2002 – 2011. 

 

33% 29% 33% 31% 31% 32% 31%

38% 40% 38%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Sprains, strains, tears

39% 34% 36% 35% 32% 35% 39% 42% 46%

41%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Nonspecified traumatic injuries

26% 27% 27% 28% 27%

34% 31% 36% 38% 36%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Other traumatic injuries

35%

42% 38% 39% 36% 35% 38% 42% 46% 44%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Non-traumatic diseases, conditions, disorders

44% 47%

35% 36% 38% 40%

47%

42%

48% 45%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Nonclassifiable + Missing

26% 29% 33% 30% 28% 32%

25%

34% 36% 32%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Multiple traumatic injuries

20% 25% 20%

30%

23% 21% 23%

31% 29% 24%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Fractures

34% 30% 30% 32% 27% 32% 27% 30%

37% 37%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Bruises, contusions
31

Multivariate regression 

Including all establishment and injury characteristics in a multivariable logistic regression model, 

survey year was still found to be significantly associated with increased underreporting for years 2002 –

2011 (Table 7). 

Table 7. Probability of unreported WA WC time loss claim by survey year, establishment and injury 

characteristics, 2002 – 2011. 

OR 95% CI Pr > ChiSq

Survey year 1.04 1.03 1.05 <.0001

SAMPLED UNIT

UI account Referent

Reporting unit 2.08 2.01 2.17 <.0001

SIZE

1-49 employees 1.24 1.17 1.32 <.0001

50+ employees Referent

INDUSTRY

Manufacturing Referent

Finance, Insurance, Real Estate 0.90 0.76 1.08 0.2661

Retail Trade 0.91 0.86 0.97 0.0044

Social Services 0.92 0.82 1.04 0.1666

Wholesale Trade 0.98 0.90 1.08 0.7345

Health Services 1.08 1.02 1.16 0.0163

Public Administration 1.09 1.01 1.18 0.0339

Transportation 1.15 1.07 1.24 0.0003

Educational Services 1.18 1.10 1.26 <.0001

Agriculture, Forestry, Fishing 1.20 1.08 1.33 0.0009

Construction 1.42 1.30 1.55 <.0001

Services (other than health, educational, social) 1.57 1.45 1.70 <.0001

Communications, Electric, Gas, Sanitary Services 4.16 3.80 4.56 <.0001

NATURE OF INJURY

Sprains, strains, tears Referent

Fractures 0.73 0.66 0.80 <.0001

Multiple traumatic injuries and disorders 0.91 0.84 1.00 0.0381

Other traumatic 0.92 0.87 0.98 0.0111

Bruises, contusions 1.01 0.92 1.11 0.8864

Non-specified traumatic injuries and disorders 1.10 1.04 1.16 0.001

Non-classifiable + missing 1.13 1.08 1.19 <.0001

Non-traumatic diseases, conditions, disorders 1.26 1.18 1.34 <.0001

EVENT OR EXPOSURE

Bodily reaction or exertion Referent

Falls 0.84 0.80 0.89 <.0001

Contact with objects and equipment 0.90 0.86 0.96 0.0004

Fire, toxics, assaults, motor vehicle accidents 0.99 0.92 1.06 0.7415

Other events or exposures 1.17 1.10 1.24 <.0001
32

KEY FINDINGS 

Between 2002 and 2011, underreporting ranged from a low of 30.6% of SOII-eligible WC time loss 

claims in 2006 to a high of 38.9% in 2010. Underreporting was found to decrease annually between 

2002 and 2006, by an estimated 0.8%. The decrease was followed by an increase in underreporting, 

between 2007 and 2011, of an estimated 2.1% annually. Despite the observed increase in 

underreporting, the total estimated number of SOII-eligible WC time loss injuries (based on reported 

and unreported claims) decreased over the ten year span. 

Between 2002 and 2011, underreporting increased most among Educational Services, 

Transportation, and Health Services. Among Retail Trade, underreporting decreased. In Wholesale 

Trade, Manufacturing, and Agriculture, Forestry, and Fishing the rate of underreporting did not change 

over the ten year period. Based on a multivariate logistic regression model controlling for survey year, 

sampled unit, establishment size, and injury characteristics, claims from establishments in eight industry 

groupings were more likely to be unreported compared to claims from manufacturing establishments: 

Health Services; Public Administration; Transportation; Educational Services; Agriculture, Forestry, 

Fishing; Construction; Services (other than health, educational and social); and Communications, 

Electric, Gas, Sanitary Services. 

Claims for injuries from bodily reaction and exertion were more likely to be unreported compared to 

injuries resulting from falls or injuries from contact with objects and equipment. Underreporting was 

found to increase over time among both injuries from bodily reaction and exertion and injuries for 

contact with objects and equipment, and remained constant for injuries from falls. 

Claims for sprains, strains, tears were more likely to be unreported compared to most other 

traumatic injuries. Non-traumatic diseases, conditions, or disorders were more likely to be unreported 

compared to sprains, strains, tears. Underreporting increased among: Sprains, strains, tears; nonspecified traumatic injuries; non-traumatic diseases, conditions, disorders. Underreporting increased 

slightly among Fractures and Multiple traumatic injuries in the same ten year time period and did not 

change for Bruises and contusions. 

AREAS FOR FUTURE RESEARCH 

This study found an increase in unreported WC claims in SOII between 2002 and 2011. Additional 

research is needed to identify the reasons for the observed increase in underreporting, e.g. economic 

forces; changes in WC claim filing propensity; or is the increase an artifact of the linking procedures, 

reflecting shifts in business structures to something more difficult to reconcile across data systems. One 

approach might be to replicate the study in other states to see if results are consistent. 

To further explore trends in underreporting, one could follow firms that participate in SOII every 

year (or almost every year) and evaluate the completeness of their reporting compared with WC claims 

data to assess patterns in their reporting. 

 
33

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Leigh, JP, Marcin, JP, Miller, TR. 2004. An estimate of the U.S. Government's undercount of nonfatal 

occupational injuries. J Occup Environ Med 46: 10-18.

Oleinick, A, Zaidman, B. 2010. The law and incomplete database information as confounders in 

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Rosenman, KD, Kalush, A, Reilly, MJ, Gardiner, JC, Reeves, M, Luo, Z. 2006. How much work-related 

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Ruser, JW, 2010. Allegations of Undercounting in the BLS Survey of Occupational Injuires and Illnesses, 

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