VLADIMIR PUTIN pointed out that the Russian currency’s recent loss of value had a silver lining. “ We earlier sold a product worth $1 and got 32 rubles for it,” he told the TASS news agency. “And now we get 45 rubles for the same product costing $1. Budget revenues have increased and not decreased.” That simple math works for big energy producers like Russia, where government revenues come mostly from sales of oil and gas for dollars. When world energy prices drop, a depreciating currency can allow a government to keep spending at home and cushion the shock. Not everyone gets it, however. Unfortunately for Venezuelans, Mr. Putin’s lesson is lost on their own leaders, who are continuing to preside over an accelerating — and dangerous — economic collapse in one of the world’s biggest petroleum powers. The price of Venezuela’s heavy oil dropped below $70 a barrel […]