Fortune | Oil Down, but Ends Year With Biggest Gain Since 2009 Fortune Oil prices have slumped since the summer of 2014 from above $100 a barrel. The price rout, due to an oversupply thanks in part to the U.S. shale oil revolution, was accentuated later that year when Saudi Arabia rejected any deal by the Organization of ... Oil on track for largest annual gain in 7 years |