Oil producers reluctant to curb output even as prices tumble to five-and-a-half year lows don’t need to guess what the future holds. They can ask a miner. In coal to iron ore markets, suppliers have raised volumes even as prices slumped, boosting global gluts and jeopardizing profits as the most dominant players seek to maintain revenue and squeeze out higher cost rivals. Prices of thermal coal , used to generate electricity, and metallurgical coal , a key ingredient in steel, have tumbled more than half since 2011 on supply additions and slowing demand in China , the biggest commodities consumer. With OPEC insistent that it won’t curb crude output, and U.S. production rising to its fastest weekly pace in more than 30 years, oil markets may be in line for similar prolonged pain. “If OPEC every now and again looks over their shoulder at what is happening in other […]