A rout in oil prices is likely to continue into the first half of 2015 unless global output is reduced, the International Energy Agency said Friday. Crude prices have fallen around 30% since June to hover near four-year lows amid sluggish demand growth and a surplus of oil supply as a result of booming production in North America. Though the IEA expects demand growth to pick up throughout next year after falling to its weakest level in five years in 2014, it forecasts demand will fall steeply at the start of 2015 compared to the end of this year. Meanwhile, robust oil supply shows no sign of abating.