The rising production of natural gas in the U.S. from shale deposits has hurt the use of thermal coal. Appalachian coal costs $65 per ton to produce and prices have dropped to $52 a ton on the spot market, making it unprofitable to produce. Coal mining companies were relying on the demand for metallurgical coal from China's steel industry, which has boomed since 2004, to continue profitable mining operations. From $40 a ton in 2004 the price of metallurgical coal climbed to $330 in 2011. In 2009 U.S. met coal exports went up to six times the prior year's production and this continued in 2010, leading to rapid expansion. Now with a slowdown in China and the Chinese steel industry operating at a loss with huge overcapacity, the prices of met coal are down to $170 a ton. Patriot Coal of St. Louis filed for bankruptcy protection and many companies are shutting down mines and laying off workers.