Oil futures plunged further on Monday to mark their lowest settlements in nearly 7 years, in the aftermath of the decision by the Organization of the Petroleum Exporting Countries last week to keep crude production running at current levels.

January West Texas Intermediate crude CLF26, dropped $2.32, or 5.8%, to settle at $37.65 a barrel on the New York Mercantile Exchange. That was the largest one-day percentage loss since September.

January Brent crude UK:LCOF6 fell $2.27, or 5.3%, to end at $40.73 a barrel on London’s ICE Futures exchange.

WTI and Brent prices, which each lost about 4.2% last week, haven’t settled at levels this low since February 2009, based on the most-active contracts.

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On Friday, WTI crude settled 2.7% lower while Brent futures lost 1.9% after OPEC, at its meeting in Vienna, agreed to maintain a ceiling that reflects “current actual production” even as the market struggles with oversupply.

“Unfortunately, the meeting just restates that OPEC is stuck to their strategy of protecting market share,” said Luana Siegfried, energy analyst at Raymond James. The decision “most likely will keep a lid on crude prices as the supply side of the supply/demand curve ... will remain glutted, not being totally absorbed by weak demand.”

OPEC previously had a production ceiling of 30 million barrels a day, but members have been producing closer to 31.5 million barrels a day, according to market estimates. Analysts have concluded that the decision essentially legitimizes the cartel’s overproduction.

“No result is also a result, and in the case of OPEC it is hard to imagine a more negative one,” said Commerzbank commodity analysts in a Monday note. “If in a critical situation OPEC cannot even agree on a lowest common denominator such as an official production limit, it is permissible to question its right to exist. In any case, the oil price looks likely to find virtually no support from OPEC in the coming months.”

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Still, the low prices do seem to be having an impact on production. Monthly data released Monday by the U.S. government showed that domestic shale-oil output is expected to fall by 116,000 barrels a day to 4.861 million barrels a day in January.

As for prices, Katrina Lamb, head of investment strategy and research at MV Financial, said there seems to be “a fairly retractable support level for WTI not too far from $40.”

She said she wouldn’t be too surprised to see occasional breaches on the downside as meeting reaction and other forces play out over the next couple of weeks or so, but a $40-$60 range is “a plausible corridor heading into next year.”

Given the “bruised emotions” following the OPEC meeting, “we can’t ignore the potential for OPEC itself ... to be a contributor to ongoing volatility,” said Lamb.

See also:OPEC squeezing shale producers, but also feels pain of oil rout

On Nymex, petroleum product prices also ended sharply lower, with January gasoline US:RBF6 down 6.1 cents, or 4.8%, at $1.209 a gallon and January heating oil US:HOF6 losing 6.3 cents, or 4.7%, to $1.28 a gallon.

See also:One benefit to plunging oil: lowest gasoline prices in nearly 7 years

January natural gas US:NGF16 ended at $2.067 per million British thermal units, down 11.9 cents, or 5.4%.