Oil plunged today below $100 a barrel, a psychological threshold that, if it holds, threatens the rulers of Russia and numerous OPEC states that rely on higher prices to mollify their populations. A critical question, then, is whether we are looking at a sustained period of lower prices or a blip before a swing back up. The price of Brent crude—the type that dominates international trade—fell as low as $99.36 today, its lowest price in 14 months. (West Texas Intermediate, the oil produced in the United States, plummeted to $91.70 a barrel, frighteningly close to its own $90 threshold.) Voices from OPEC said they are not alarmed and that prices will go back up over the next few months when Winter demand commences. Bernstein’s Oswald Clint told Quartz that the long-term trend is for prices to rise, supported by higher costs to produce oil and constrained supply. But there is reason for OPEC members […]