Professor Alison Morantz’s working paper on whether union coal mines are safer than non-union operations is featured in this story by Daniel Malloy of the Pittsburgh Post-Gazette.

A new study shows that unionized underground coal mines have sharply lower serious injury and fatality rates than non-union mines.

Funded by a contract from the National Institute of Occupational Safety and Health and published last week by Stanford law school professor Alison D. Morantz, the report adds data-driven heft to claims often made by the United Mine Workers and union allies. They contend that additional eyes from union safety councils and protections for workers to voice concerns about unsafe conditions have a demonstrable positive effect on mine safety.

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Looking at underground bituminous coal mines from 1993 to 2008, Dr. Morantz found that unionization results in an 18 to 33 percent drop in traumatic injuries and 27 to 68 percent drop in fatalities. Meanwhile, union mines had higher rates of non-traumatic injuries, which the author said was likely because non-union mines reported fewer of them.

“I find that unionization predicts a sizable and robust decline in both traumatic injuries and fatalities, the two safety outcomes that I argue are least prone to reporting bias,” Dr. Morantz wrote. “At the same time, I find that unionization predicts higher total and non-traumatic injuries, lending credence to claims that injury reporting practices differ significantly between union and nonunion mines.”

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Previous studies, Dr. Morantz wrote, found no relationship between unions and mine safety in previous decades.

In her study, Dr. Morantz controlled the results for the size of the mine, the state where it was located, its productivity and how it extracted coal, among other factors.

Over the 15-year period of the study, the unionization in the mines Dr. Morantz surveyed dropped by more than half, to 9.6 percent in 2008. Also over that time, the number of traumatic injuries stayed flat while total injuries declined steadily — in union and nonunion mines.