The government says that the number of chronic safety violators among mine operators has fallen sharply in recent years.

The Mine Safety and Health Administration says the number has dropped in response to reforms the agency has taken to rein in bad actors. The National Mining Association counters that the industry's own safety program deserves the credit.

In its 2010 screening, 51 chronic violators were identified for further review among mine operators. But for this year's screening, that number had dropped to 12. The biggest reduction came in coal mines, which dropped from 42 in 2010 to six this year.