One wild card for the markets in 2018 is the Federal Reserve. Jerome Powell is set to succeed Janet Yellen as Chair in February and the central bank is also in the process of unwinding its multi-trillion dollar balance sheet.

"We had a record run rate in quantitative easing - $2 trillion poured into these markets," said Danielle DiMartino Booth, author of Fed Up. "There's no head scratching about why markets are at record levels."

If the Fed and the European Central Bank stick to their plans of winding down stimulus, total QE entering the markets is expected to drop to only $1 trillion in 2018, according to Booth.

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