Hedge funds boosted bearish wagers on oil to a four-year high as U.S. supplies grew the most since 2001.

Money managers increased short positions in West Texas Intermediate crude to the highest level since September 2010 in the week ended Jan. 20, U.S. Commodity Futures Trading Commission data show. Net-long positions slipped for the first time in three weeks.

U.S. crude supplies rose by 10.1 million barrels to 397.9 million in the week ended Jan. 16 and the country will pump the most oil since 1972 this year, the Energy Information Administration says. Saudi Arabia’s King Salman, the new ruler of the world’s biggest oil exporter, said he will maintain the production policy of his predecessor despite a 58 percent drop in prices since June.

“There’s been a rush to call a bottom,” John Kilduff, a partner at Again Capital LLC, a New York-based hedge fund that focuses on energy, said by phone Jan. 23. “The fundamentals are still stacked against a rebound.”

WTI rose 50 cents, or 1.1 percent, to $46.39 a barrel on the New York Mercantile Exchange during the CFTC report period. The U.S. benchmark fell 25 cents to $45.34 at 9:22 a.m. Brent slipped 30 cents to $48.49.

Salman Bin Abdulaziz Al Saud ascended to the throne after King Abdullah died last week. The kingdom pumped 9.5 million barrels a day in December as members of the Organization of Petroleum Exporting Countries exceeded their 30 million-barrel daily target for a seventh month.

U.S. Production

“I don’t see any major catalyst from either the supply or demand side that will send prices higher this year,” Stewart Glickman, an equity analyst at S&P Capital IQ in New York, said by phone Jan 23. “It looks like $50 crude is the new reality that we’ll have to get used to.”

Production in the U.S. will be slow to decline as improvements in drilling technology boost well output even as companies drill less. Oil production per rig from new wells in the Bakken in February will be double what it was three years ago, the EIA said Jan. 12.

The nation’s oil boom has been driven by a combination of horizontal drilling and hydraulic fracturing, or fracking, which has unlocked supplies from shale formations including the Eagle Ford and Permian in Texas and the Bakken in North Dakota.