(Bloomberg) -- Investors skeptical that OPEC would cut output fled the market after the group came to an agreement.

Money managers slashed bets on lower West Texas Intermediate crude prices by the most in five years after OPEC's Nov. 30 accord to reduce supply. The deal sent futures to a 16-month high, which some U.S. shale producers used as an opportunity to hedge their own output. Prices are extending gains this week after Saudi Arabia signaled Saturday it would make deeper cuts than expected just after Russia and other non-OPEC countries pledged to curtail production next year.

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