Marcellus Shale natural gas prices are monthly average of $2.80 per million BTU compared to benchmark U.S. prices for natural gas of $3.61 in Nov. 2013. The low prices of natural gas are leading to closing of more coal powered plants in the Pennsylvania, and W. Virgina, where a glut of natural gas is developing with few pipelines in the region. For the U.S. coal lost market share down to 37% in 2012 from about 50% of the electricity generated in the U.S. Over 100 coal burning generators were closed in the U.S. since 2011 because of lower natural gas prices and the federal government's stricter pollution limits for power plants.