It's hard to come up with an answer to what might cause the next crash. A credit downgrade to junk status on US debt might be a good start. That's entirely plausible given the huge tax cuts and resulting drop in tax revenues spawning the extreme unlikelihood the US budget deficit being brought under control or ending the expansion of our national debt.
A look at $SPX 10 year chart shows what could be the beginning of a bump and run. If the CEOs bold enough to come out and actually say what their real intentions were to do with repatriated profits stick to their plans to buy back stock and increase dividends, and the CEOs keeping quiet but intending to do the same, the S&P and the rest of market could go parabolic for while. That'll draw in the last of the noobs just in time for the slaughter.
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