According to data from the US Energy Information Administration, annual coal sales from those areas totaled 458 million to 509 million tons from the 2003 fiscal year to financial year 2012, which begins October 1 of each year.

Production from federal and Indian lands in the state were between 356Mt and 411Mt over the same period, or about 76% to 83% of the US total.

Wyoming PRB mines are among the largest in the country and, as EIA experts noted, most of the coal mined in the Wyoming portion of the PRB were located on those lands.

“Using these sales as a proxy for production, Wyoming's federal and Indian lands production has been about 82% to 95% of Wyoming's total production over the past decade,” the agency said.

The numbers have been positive from a revenue perspective as well. The state has collected a low of $303 million in FY 2003 to a high of $638 million last fiscal year from coal sales made from federal and Indian lands.

Under federal regulations, 49% of all onshore federal land production goes to the state directly, and 100% of revenue associated with Indian lands goes to the respective Indian tribes and individual Indian mineral owners.

Wyoming has not been immune to the market downturn, according to EIA’s data takers. Between FY2008, when coal production in Wyoming was at a record high level, and FY2012, coal production in the state declined 10% while coal sales and production from federal and Indian lands fell 9% at the same time.

The decline in FY2009, the agency said, was attributable to the economic downturn that in turn reduced electricity demand.

When the decline continued through the past fiscal year, the drop reflected slow growth in electricity demand and coal’s reduced share in the generation mix stemming from competition with other generation types.