Production of US shale oil will fall sharply next year as a result of the collapse in crude prices, the world’s leading energy forecaster said on Friday, in a sign that Saudi Arabia’s attempt to squeeze higher-cost producers out of the market is succeeding. The prediction was made by the International Energy Agency in its closely watched monthly oil market report, which said the collapse in oil prices since June last year had “slam[med] the brakes” on the US shale industry. The IEA said oil production outside Opec, the producers’ cartel, would decline by nearly 500,000 barrels a day next year, the largest drop since the collapse of the Soviet Union. US shale oil will account for about 80 per cent of that fall. The US industry has so far proved surprisingly resilient in the face of low oil prices, which last month hit their lowest level since the global financial crisis. But the IEA report suggests the growing financial pressure on shale operators and the steep fall in the number of rigs drilling for oil is beginning to take their toll on production.