The Stock Market Is Flashing a Rare Warning Signal. Here's How History Says Investors Should Prepare.

The S&P 500 index (SNPINDEX: ^GSPC) has been on a marvelous run. In the past decade, it has generated a total return of 321% (as of Sept. 18). Had you invested $10,000 in September 2016 in an exchange-traded fund (ETF) tracking the benchmark, you'd have $42,100 today. From a historical perspective, this is exceptional. If you had a strong allocation to equities during this time, then you're not complaining at all. But it's worth understanding the present situation clearly. This way, you can set the right expectations about what the future might bring. Missed AI's "Act 1"? Act 2 Could Be 15x Bigger. Most investors think they missed the AI boat because they didn't buy Nvidia in 2005.