2010 to 2013 according to former industry executives, analysts and consultants. The cause of this was alleged to be Goldman's ownership of a quarter of the national supply of aluminum – a million and a half tons – in network of 27 Metro International warehouses Goldman owns in Detroit, Michigan. To avoid hoarding and price manipulation, the London Metal Exchange requires that "at least 3,000 tons of that metal must be moved out each day". Goldman has dealt with this requirement by moving the aluminum – not to factories, but "from one warehouse to another" – according to the Times. In August 2013, Goldman Sachs was subpoenaed by the federal Commodity Futures Trading Commission as part of an investigation into complaints that Goldman-owned metals warehouses had "intentionally created delays and inflated the price of aluminum". In December 2013, it was announced that 26 cases accusing Goldman Sachs and JPMorgan Chase, the two investment banks' warehousing businesses, and the London Metal Exchange in various combinations – of violating U.S. anti-trust laws, would be assigned to United States District Court for the Southern District of New York Judge Katherine B. Forrest in Manhattan. According to Lydia DePillis of Wonkblog, when Goldman bought the warehouses it "started paying traders extra to bring their metal" to Goldman's warehouses "rather than anywhere else. The longer it stays, the more rent Goldman can charge, which is then passed on to the buyer in the form of a premium." The effect is "amplified" by another company, Glencore, which is "doing the same thing in its warehouse in Vlissingen". Michael DuVally, a spokesman for Goldman Sachs, said the cases are without merit. Columnist Matt Levine, writing for Bloomberg News, described the conspiracy theory as "pretty silly", but said that it was a rational outcome of an irrational and inefficient system which Goldman Sachs may not have properly understood. In December 2014, Goldman Sachs sold its aluminum warehousing business to Ruben Brothers. Oil futures speculation Investment banks, including Goldman, have also been accused of driving up the price of gasoline by speculating on the oil futures exchange. In August 2011, "confidential documents" were leaked "detailing the positions" in the oil futures market of several investment banks, including Goldman Sachs, Morgan Stanley, JPMorgan Chase, Deutsche Bank, and Barclays, just before the peak in gasoline prices in the summer of 2008. The presence of positions by investment banks on the market