Heavyweight oil producer group OPEC stepped into the ring with young upstart US shale back in November 2014 and delivered its best shot. Led by prizefighter Saudi Arabia, it decided not to cut output in hopes of arresting the slide in prices, but, in an attempt to floor the relatively high-cost producer, declared it would defend its ground. Fast forward 13 months and unconventional crude supply is down but not out. And OPEC, whose membership has been split down the middle by a policy aimed at clawing back market share from what has proved to be a resilient opponent, must be wondering whether it has all been worth it — especially after having read the International Energy Agency’s latest medium-term forecasts. The IEA expects US light tight oil output to start recovering in 2018 after a 600,000 b/d decline in 2016 and a further 200,000 b/d drop next year. […]