The Declining Effects of OSHA Inspections on Manufacturing Injuries: 1979 to 1998

This study compares the impact of OSHA inspections on manufacturing industries using data from three time periods: 1979-85, 1987-91, and 1992-98. We find substantial declines in the impact of OSHA inspections since 1979-85. In the earliest period we estimate that having an OSHA inspection that imposed a penalty reduces injuries by about 15%; in the later periods it falls to 8% in 1987-91 and to 1% (and statistically insignificant) in 1992-98. Testing for different effects by inspection type, employment size, and industry, we find differences across size classes, but these cannot explain the overall decline. In fact, we find reductions in OSHA's impact over time for nearly all subgroups we examine, so shifts across subgroups cannot explain the whole decline. We examine various other hypotheses concerning the declining impact, but in the end we are not able to provide a clear explanation for the decline.