The dot-com bubble popped 25 years ago. Here's what market pros say they learned.

The Nasdaq Composite peaked connected March 10, 2000 and the consequent unwind would past astir 3 years, taking the tech-heavy scale down 78% astatine its debased successful October 2002.

Fast-forward 25 years and investors are wondering whether the advent of artificial quality has catapulted markets backmost into bubble territory.

With the Nasdaq down 13% successful the past month, the caller banal sell-off has immoderate investors wondering if this is the opening of a overmuch longer and much achy correction aft years of bullish exuberance. Sound familiar?

Here's what investors and strategists told Business Insider astir immoderate of the hard-learned lessons from the dot-com crash.

Whether you're looking astatine the Dutch tulip bubble of the 1630s oregon the Japanese existent property bubble of the 1980s, each marketplace cycles acquisition the aforesaid phases that investors should beryllium alert of.

Ted Mortonson, managing manager and exertion specializer astatine Baird, told BI those chiseled phases see overexuberance, complacency, concern/fear, panic, and capitulation.

"Until each signifier of the rhythm is experienced, bottoms cannot occur," Mortonson said.

Mortonson estimates that the existent marketplace rhythm is successful the concern/fear zone, suggesting that determination is much downside ahead.

"We volition merchantability disconnected materially successful aboriginal April connected maturation deceleration fears," Mortonson said, adding that first-quarter net results volition beryllium riddled with misses and lowered guidance amid ongoing uncertainty astir President Donald Trump's commercialized policies.

According to Giuseppe Sette, president astatine Reflexivity, banal valuations should beryllium intimately monitored by investors.

The guardant price-to-earnings ratio of the S&P 500 peaked astatine astir 24x successful 2000. It precocious approached those levels but rapidly retreated, topping retired astatine astir 23x successful 2021 and past again earlier this year.

"The dot-com bubble and 2021 unneurotic amusement that 23x-24x guardant P/E is arsenic overmuch arsenic the marketplace is capable to sustain," Sette told BI via email. "Every clip you spot 22.5x P/E, a drawdown is near."