Occupational injuries: factors associated with frequency and severity.

In recent years, energy exchange has come to be accepted as the causative agent in accidental injuries. This paper focuses on two fundamental characteristics of accidental workplace injuries, their frequency, and their severity. I propose that the frequency of injuries is determined largely by the nature of the interactions between workers and production processes, while the severity of the occurring injuries will be more strongly affected by the maximum possible harm the production process can cause. Other aspects of the design of the production process may also affect the severity of injuries. Using aggregate national data for manufacturing industries in the US for 1972, the rate of injuries per 100 employees per year and the average number of lost work days per injury (a common measure of severity) were regressed against a number of econometric variables. Eighty percent of the variation in injury frequency rates among 61 industries was explained by seven variables. Among them were the rate of new hires, the productivity of energy and of labor, the average hourly wage, and the percentage of the workforce that was unionized. Four variables explained 69% of the variation in the severity of injuries among industries. Nearly half of this effect was caused by just one variable, the amount of energy consumed per worker. These results provide tentative confirmation for the models of injury frequency and severity that were proposed, and suggest the need for another study using less aggregated data.