These rates are calculated based on hours of miners’ exposure, a relative measure taking into account recent employment changes in the mining market.

In 2015, 28 miners died in mining accidents, down from 45 in 2014. The fatal injury rate, expressed as reported injuries per 200,000 hours worked, was the lowest in mining history for all mining at 0.0096, down from 0.0144 in 2014 and 0.0110 in 2011 and 2012.

The fatal injury rate for coal mining in 2015 was 0.0121, the lowest rate ever. The previous fatal injury rate low was set in 2011, during a period of peak employment in the coal industry.

In the metal and nonmetal mining industry, both the number of fatalities and the fatal injury rate were cut almost in half from the previous year’s figures. The fatal injury rate of 0.0085 was close to the all-time low of 0.0079 set in 2012.

The all-injury rate – reported by mine operators – also dropped to a new low in 2015 at 2.28. Coal’s all-injury rate fell to 2.88, the first time it dropped below 3.0. Metal and nonmetal’s all-injury rate fell to a new low of 2.01.

Assistant secretary of labor for mine safety and health Joseph Main said: “The progress we made in 2015 is good news for miners and the mining industry.

“It is the result of intensive efforts by MSHA and its stakeholders that have led to mine site compliance improvements, a reduction of chronic violators, historic low levels of respirable coal dust and silica, and a record low number of mining deaths.”

The numbers of miners and mining operations were down in 2015, and accordingly, MSHA conducted fewer inspections. Even accounting for the decline in the number of mines, compliance improved, demonstrated by an 11% reduction in the number of citations and orders issued.

Assessments of penalties dropped to $US62.3 million in 2015, with approximately 2% of violations not yet assessed.