With world oil inventories swelling despite a global pact on cutting output and crude prices falling by a fifth in the past month, OPEC appears to be losing its battle to balance the market. But there is one crucial fight the oil-exporting group has been winning so far: its members have earned more money this year than last and the prospect of higher revenues is likely to motivate OPEC to stick with output cuts or even deepen them. OPEC’s first output cut in eight years has earned the group $1.64 billion a day so far this year, up more than 10 percent from the second half of 2016, according to Reuters calculations based on OPEC figures for average production and […]