Oil futures ended under $47 a barrel Thursday after a weekly supply report showed an increase in crude inventories that was four times larger than Wall Street expected, sending U.S. crude stockpiles to their highest level in eight decades. The U.S. Energy Information Administration said crude inventories rose by 10.1 million barrels on the week ended Jan. 16. Analysts polled by Platts had expected an increase of 2.5 million barrels. Moreover, at 387.9 million barrels, U.S. crude oil inventories “are at the highest level for this time of the year in at least the last 80 years,” the EIA said in the report. One would have to go back to the Calvin Coolidge administration to see U.S. supplies hovering at 400 million barrels, and the surge this week was attributed to lower refinery runs.

On the New York Mercantile Exchange, light, sweet crude futures for delivery in March fell $1.47, or 3.1%, to $46.31 a barrel. The contract had traded at $47.14 a barrel moments before the supply report was released. Brent for March delivery lost 51 cents, or 1%, to $48.52 a barrel on London’s ICE Futures exchange. A global supply glut and lackluster demand is at the root of oil’s rout. Oil futures have lost 58% from a 2014 peak at $107.26 in June. Analysts have said they expect the oversupply in oil markets to persist through at least the first half of the year, and there’s no indication the Organization of the Petroleum Exporting Countries or producers outside the cartel would move to cut down on output. Several energy companies have announced capital-budget cuts for this year and some have announced layoffs due to the lower prices, but not significant production cutbacks. While shutting down a well could be a relatively straightforward maneuver from a technical standpoint, companies are restricted by intricate lease regulations and investment commitments, among other considerations that must be made before pulling the plug on a well.

Gasoline stockpiles increased by 600,000 barrels, while distillates inventories declined by 3.3 million, the EIA said. The analysts surveyed by Platts had expected gasoline stocks up 1.05 million barrels and distillate stocks, which include heating oil, up 167,000 barrels.

Prices had seesawed earlier in the session, as investors digested news that the European Central Bank will buy 60 billion euros a month in government bonds, starting in March and continuing at least through September 2016. The move is aimed at spurring growth and fending off deflation in the region. Crude-oil futures rallied Wednesday on the news the ECB would announce the package, which fanned hopes that demand for crude oil would soon increase.

In the short term, however, the ECB’s decision will further weaken the euro and make dollar-denominated commodities like oil more expensive for holders of the common currency. In the longer term, if the stimulus does accelerate the sluggish eurozone economy, this would help improve crude demand in the region, analysts at Phillip Futures said in a note.