Ruser, J. & Smith, R. (1991). Re-estimating OSHA’s effects: Have the data changed? Journal of Human Resources, 26(2), 212-235.
- The study’s objective was to determine the effect of OSHA inspections and inspection procedures on injury rates in manufacturing firms between 1980 and 1985. Although OSHA no longer operates as it did during this period, this study provides historical context for changes that were later made to the program.
- For their main analysis, the authors used a regression model to compare differences in injury rates for manufacturing plants that received inspections in March and April (“early”) and those that received inspections in November and December (“late”) of the same year.
- The study found that, relative to late OSHA inspections, early OSHA inspections were not associated with a statistically significantly reduction in injury rates within the year of inspection.
- The quality of the causal evidence presented in this study is low. This means we are not confident that the estimated relationships in this study are the result of OSHA inspections and procedures.
OSHA Enforcement Activities
Types of and Outcomes
For its main analysis, the study examined the effect of OSHA inspections on lost-workday injury rates in manufacturing firms between 1980 and 1985. Although OSHA no longer operates as it did during the period examined, this study provides historical context for changes that were later made to the program. The study also considered the impact of OSHA’s record-checking procedure, initiated in 1981, on lost-workday injury rates. Under this procedure, inspections by OSHA of firms in manufacturing industries with above average lost-workday injury rates (dubbed “high-risk”) followed a two-step procedure. First, a compliance officer would inspect an establishment’s records to determine past-year injury rates. If the injury rate exceeded a threshold, the establishment was then inspected in full. Otherwise, the planned inspection was terminated.
Features of the Study
The study used a regression model to examine differences in injury rates for firms that received inspections in March and April and those that received inspections in November and December of the same year. To determine the impact of being subject to the records-check procedure, the model included an indicator for the establishment’s industry having been designated as “high-risk,” an indicator for the records-check procedure being in place, and the interaction of these variables. The model also included controls for the lost-workday injury rate in the prior year, changes in employment over time, establishment size, two-digit industry classification, and year. The analyses were based on data from the Bureau of Labor Statistics Annual Survey of Injuries and Illnesses, the Federal OSHA Management Information System, and County Business Patterns publications on 4,114 manufacturing establishments inspected by state or federal OSHA regulators in March, April, November, or December between 1980 and 1985.
- Relative to late OSHA inspections, early OSHA inspections were not associated with a statistically significant reduction in injury rates within the year of inspection.
- There was no evidence that the records-checking procedure led to differences in the reported injury rates.
Considerations for Interpreting the Findings
In this study, the authors argued that, given that a firm is inspected, the time of year in which it is inspected is likely random. However, in 1978, OSHA developed a system for conducting inspections based on administrative data. This system prioritized inspections at potentially more dangerous firms over the course of the year. Thus, firms inspected earlier in the year might have been more hazardous than those inspected later in the year. In addition, firms subject to the records-checking procedure might differ from those that would be inspected using different procedures. In particular, the records checking procedure was used only in states where OSHA inspections were federally-administered. Therefore, it is unclear whether the lack of statistically significant findings reflects a true lack of association between inspections and injury rates or is attributable to differences between the groups being compared.
Causal Evidence Rating
The quality of the causal evidence presented in this study is low. This means we are not confident that the estimated relationships in this study are the result of OSHA inspections and procedures. To provide more convincing causal evidence that meets CLEAR criteria, the study would need to show that the groups compared (establishments inspected early and late in the year, or establishments subject to the record-check procedure and those not subject to it) experienced similar trends in injury rates before the intervention of interest occurred.