Crude oil storage space became a tradable commodity with CME Group— which owns NYMEX— offering oil-storage futures contracts in March 2015.[6] Many participants—including Wall Street giants, such as Morgan Stanley, Goldman Sachs, and Citicorp—turned sizeable profits simply by sitting on tanks of oil.Trafigura, Vitol, Gunvor, Koch, Shell and other major energy companies began to book oil storage supertankers for up to 12 months.[7] The United States Strategic Petroleum Reserve (SPR) is the world's largest supply of emergency crude oil—727 million barrels— stored in huge underground salt caverns along the coastline of the Gulf of Mexico.The SPR is a "deterrent to oil import cutoffs and a key tool of foreign policy" but it has rarely been used.