The S&P 500's Shiller price-to-earnings ratio has climbed to 42.2, its highest level since the dot-com bubble peaked at 44.2 in November 1999. The reading sits far above the index's long-run average, with much of the market's expensiveness driven by the current AI boom and heavy concentration in a handful of mega-cap stocks, according to The Motley Fool.
The S&P 500 hasn't been this expensive in more than 26 years. Its cyclically adjusted price-to-earnings ratio, known as the CAPE ratio, now stands at 42.2, approaching the 44.2 level it hit at the height of the dot-com bubble.
A valuation last seen in 1999
The CAPE ratio measures S&P 500 companies' earnings over the past decade, adjusted for inflation, to strip out one-off distortions such as the COVID-19 lockdown. The average CAPE ratio since the start of 1990 sits at just over 27, underscoring how stretched the current market has become relative to its own history.
At the peak of the dot-com bubble in March 2000, the S&P 500 topped out at 1,527 points before losing half its value over the following two and a half years. That collapse left many companies bankrupt and wiped out investor portfolios.
Why this cycle looks different
The comparison isn't a straight one, however. Many dot-com-era companies had little revenue and no profit, whereas today's most expensive stocks are concentrated in a handful of "Magnificent Seven" names that are highly profitable and central to the artificial intelligence buildout. Investors are willing to pay a premium for that growth, even as debate continues over whether the AI trade itself has become a bubble.
What history suggests for investors
Past results don't guarantee future performance, and assuming this cycle will end exactly like the last one risks encouraging investors to time the market. The Motley Fool's Stefon Walters instead recommends dollar-cost averaging — investing a fixed amount on a set schedule regardless of conditions — as a way to stay invested through any pullback without trying to call the top.
Source: The Motley Fool
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