The S&P 500 Is Flashing a Warning Sign Not Seen Since the Dot-Com Bubble. Here's What History Says Investors Should Do.

The AI roar has lifted the banal marketplace to caller heights, with the S&P 500 (SNPINDEX: ^GSPC) doubling successful the past 4 years alone.

However, tech stocks person been shaky successful caller weeks, causing volatility successful the broader market. The tech-heavy Nasdaq Composite (NASDAQINDEX: ^IXIC) is down much than 4% from its high, arsenic of this writing, portion the PHLX Semiconductor Index is nearing carnivore marketplace territory, having fallen astir 19% from its peak.

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Recent turbulence has renewed fears surrounding an AI bubble. Around 43% of money managers judge AI stocks are successful a bubble, according to Bank of America's astir caller Global Fund Manager Survey, compared with 48% who don't.

While that doesn't needfully mean that a dot-com-like clang is looming, the banal marketplace is sounding a akin informing close now. Here's what that means for your investments.

Valuations are reaching historical levels

The S&P 500 Shiller CAPE Ratio measures the S&P 500's 10-year inflation-adjusted net to gauge the index's valuation implicit time. Because it uses a decade's worthy of data, it provides a much implicit representation of however the scale has changed done aggregate marketplace cycles.

A higher metric suggests the scale is trading astatine a premium and possibly overvalued, portion a little fig implies it's undervalued. The S&P 500 Shiller CAPE ratio's semipermanent mean is astir 17, and it's been steadily creeping higher implicit the past decennary oregon so.

Right now, the ratio is nearing 42 -- the highest it's been since the dot-com bubble, erstwhile it peaked astatine astir 44.

The Shiller CAPE Ratio has stayed supra 40 since May, which is lone the 2nd clip successful past that it's remained this high. The archetypal clip was successful January 1999, erstwhile it stayed supra 40 until September 2000.

During that time, however, the marketplace itself was not needfully showing immoderate glaring reddish flags. The S&P 500 surged by astir 24% betwixt January 1999 and September 2000, portion the Nasdaq astir doubled implicit that period.

In hindsight, however, the dot-com bubble was already popping. The carnivore marketplace officially began successful March 2000, and betwixt past and October 2002, the S&P 500 and Nasdaq plunged by astir 49% and 78%, respectively.

No metric is perfect, and past show can't foretell aboriginal earnings. But it's uncommon for the marketplace to beryllium this richly valued, truthful if there's 1 takeaway for investors close now, it's that choosing the close investments is much captious than ever.