Inside the Black Box: How Do OSHA Inspections Lead to Reductions in Workplace Injuries? (Mendeloff & Gray 2005)
Mendeloff, J., & Gray, W. (2005). Inside the black box: How do OSHA inspections lead to reductions in workplace injuries? Law and Policy, 27(2), 219-237.
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- The study’s objective was to examine the effects of OSHA inspections that resulted in penalties or citations on the types of injuries workers suffered.
- The study used a regression model to compare the changes in workplace injuries of manufacturing firms that had received an inspection that resulted in a penalty or citation to those that had not received a penalty or citation. The group of firms that had not received a penalty or citation combined two types of firms: firms that had not been inspected and firms that received inspections that did not result in a penalty or citation.
- The study found that OSHA inspections that resulted in a penalty were associated with statistically significant decreases in lost-workday injuries. Among the specific citations studied, citations for the standards for general requirements for personal protective equipment and general machine guarding were associated with statistically significant reductions in some types of lost-workday injuries.
- The quality of the causal evidence presented in this study is low. This means we are not confident that OSHA inspections that resulted in penalties or citations caused the reductions in workplace injuries.
OSHA Enforcement Activities and Outcomes
The study examined the effects of OSHA inspections that resulted in a penalty or citation at any time in the past four years on the rates of different types of workplace injuries that resulted in an employee taking one or more days away from work. The study also examined the effects of inspections resulting in specific citations, including those related to machine guarding, personal protective equipment, electrical wiring, forklift trucks, and fire extinguishers. Injuries were classified by type and examined based on their relationship to OSHA standards: struck by, caught in, high fall, eye abrasion, and toxic exposure were classified as “related to standards,” and exertion, struck against, and fall same level were classified as “unrelated to standards.”
Features of the Study
The study used a regression model to compare the changes in workplace injuries of manufacturing firms that had received an inspection that resulted in a penalty to those that had either not been inspected or had been inspected but had not received a penalty. For the analysis of specific citations, the study used a similar model to compare the changes in workplace injuries in manufacturing firms that had received an inspection that resulted in a citation for a specific type of violation to firms that had either not been inspected or that had received an inspection that did not result in this type of citation. The models included controls for changes in employment, changes in hours, industry, and year. The models did not distinguish between firms that were not inspected and those that were inspected but did not receive a penalty or citation.
The authors used confidential plant-level data from the Bureau of Labor Statistics Survey of Occupational Injuries and Illnesses, as well as inspections data from the OSHA Integrated Management Information System, for 16,036 manufacturing plants in the United States between 1992 and 1998.
- OSHA inspections that resulted in a penalty were associated with statistically significant decreases in lost-workday injuries, both for injury types believed to be related to OSHA standards (1.8 percent per year for four years) and for injury types believed to be unrelated to OSHA standards (2.8 percent per year for four years).
- Citations for violating the general requirements for personal protective equipment and machine guarding were associated with statistically significant decreases in some types of lost-workday injuries.
Considerations for Interpreting the Findings
In this study, the estimated differences between firms in the changes in injury rates may not be caused by the inspections, penalties, and citations. The differences in injury rates could reflect underlying differences in safety levels or other factors between the firms being compared. For example, about 32 percent of the OSHA inspections from 1990 to 1998 were triggered by a complaint of a workplace hazard. Therefore, the firms that received inspections likely had more underlying workplace hazards, on average, than firms that were not inspected. Similarly, firms that received a penalty or citation likely had more egregious safety violations than those that were inspected and did not receive a penalty or citation. In the absence of inspections, firms with more hazards and safety violations may have experienced different changes in injury rates as conditions deteriorated or because management would have made improvements to address unsafe working conditions.
Causal Evidence Rating
The quality of the causal evidence presented in this study is low. This means we cannot be confident that the reductions in injury rates were caused by the OSHA inspections, penalties, or citations. To provide more convincing causal evidence that meets CLEAR criteria, the study would have to examine only firms that received penalties at random or use some underlying random variation in the receipt of penalties.