Tight oil's surge poses a familiar dilemma for Opec

The rebalancing effort is on shaky ground. To keep cutting is a problem but to stop might be just as bad

American tight oil growth has surprised Opec again. The group's own forecasts for non-Opec supply have been well short of the reality. When Opec's secretariat publishes its market report next week expect another upgrade. But a change of policy is unlikely. Each option is fraught. The latest forecast, from February, predicted non-Opec supply would rise by 1.4m barrels a day in 2018. It was wishful thinking. The Energy Information Administration says US supply on its own will rise by that much, to say nothing of Brazil, Canada, Kazakhstan and others. In Houston for CERAWeek, the International Energy Agency's chief Fatih Birol said non-Opec would meet most of the world's extra demand needs over