Among the regions tracked by the EIA, the Powder River Basin (PBR) in Montana and Wyoming saw the largest decline both in terms of absolute tonnage and as a percentage of the previous quarter.

Demand for coal has dropped off steeply as natural gas becomes the primary fuel source for electrical generation. Electricity generation accounts for more than 90 percent of domestic coal use, but environmental regulations have caused the fuel source to fall out of favor. Compounding the problem for coal producers, electricity demand is growing more slowly, while historically-low natural gas prices are making it easier for electricity generators to switch to the cleaner burning fuel, reports the EIA.