Global stocks, as measured by the MSCI World Index, have been up every month so far in 2017, according to Jeffrey Kleintop, global chief investment strategist at Charles Schwab.
"We've never seen that before in the 30 year history of the index," he said.
The gains have left some investors wondering how much longer the bull market can last. Kleintop points to the looming risk of an inverted yield curve, which has accurately predicted bear markets and recessions in the past.
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