Reported emissions from the Underground Coal Mines sector decreased from 41 million metric tons (MMT) CO₂e in 2011 to 35 MMT CO₂e in 2018, a decline of 14.2 percent.  The declining trend in emissions is attributed to a nationwide decrease in coal production combined with the idling or closure of several large, gassy underground mines.  Also, emissions at some mines increased where low natural gas prices resulted in venting of coal mine methane rather than processing and selling the gas into natural gas pipelines. During this period, the number of reporters decreased from 117 in 2011 to 74 in 2018.  The decrease in the number of reporters is largely due to the closure of several mines but is also attributed to 2016 amendments in Part 98 allowing underground coal mines to cease reporting for abandoned mines. Prior to 2016, owners and operators were required to continue reporting for up to three years following abandonment.