Supply, demand and expectations are the factors that influence the oil price. In 2014 demand sagged—the result of weak economic activity and greater efficiency—while supply surged, chiefly thanks to the shale boom in America. The US now produces more than 8m barrels a day (b/d). That put OPEC, the old oil-producers’ cartel, in a pickle. Saudi Arabia and its Gulf allies are its richest members and have the lowest extraction costs. They refused to cut production from OPEC’s 30m b/d limit to bolster the price, fearing (rightly) that the result would be lost market share and a windfall for enemies such as Iran and Russia. The low price—now $53-57 a barrel, depending on your benchmark—is already dampening investment, especially in high-cost projects. That may tighten supply and eventually send the price up again. But expectations have settled. Shifting them will take time.​