Following Wall Street's worst week since the financial crisis, U.S. markets slid again during a short session on Monday before the exchanges closed for the Christmas holiday. The Dow dropped more than 640 points to below 22,000 — its worst Christmas Eve trading ever — and the S&P 500 entered a bear market. The jitters followed Treasury Secretary Steven Mnuchin's attempts to reassure investors by confirming with U.S. banks on Sunday that they were still able to make loans. When stocks briefly began to recover Monday, a tweet from President Trump claiming "the only problem our economy has is the Fed" sent them tumbling once more.

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