Can working hour reduction save workers?

•We estimate the causal impact of working hours on industrial injury rates.•We exploit a natural experiment of standard hour reduction in South Korea.•A one-hour decrease in actual working hours decreases the injury rate by 8%.

Long working hours are considered as one of the major risk factors for workplace accidents and workers' health. In this paper, we estimate the causal effect of working hours on industrial injury rates. We exploit a quasi-natural experiment in South Korea, where standard hours were reduced at different times by industry and establishment size from 2004 to 2011. We find that a one-hour reduction in weekly working hours significantly decreases the injury rate by about 8%.