Actually, from a supply and demand perspective it doesn't; at least from the public pronouncements of those in the industry. What it does do is make the commodities traders nervous and anxious to get as much as they can to maximize profits. A person who spends a fair bit of time studying the stock and commodities markets quickly comes to the correct conclusion they are tied to the actual economy by the equivalent of a loose rubber band. In most ways they are effectively legalized gambling that depends on the "greater fool" theory to make money. And changes in the actual economy do affect them. But, most of the price movement has more to do with jockeying among the traders than anything real.