S&P 500 CAPE ratio exceeds 40, a first since the dot-com peak

The Shiller CAPE ratio has remained above 40 for several months, a valuation level reached only once in 155 years of stock market data during the dot-com bubble peak. This metric, which compares the S&P 500's price to its inflation-adjusted average earnings over the previous decade, currently stands well over twice its long-term average of 17.4. The all-time high for the ratio was recorded in December 1999 at 44.2, shortly before the market lost nearly half its value.

Despite the elevated valuation, the S&P 500 is still up approximately 12% this year. However, the index has fallen nearly 2% from its record set earlier this month, driven by sticky inflation and rising bond yields. The tech-heavy Nasdaq Composite has seen a sharper pullback, dropping more than 4% from its high. Rising yields particularly impact high-growth tech stocks that are increasingly tapping debt markets, with the sustainability of the artificial intelligence spending boom keeping investors on edge.

Another indicator of market expense is the ratio of U.S. stock market value to gross domestic product, a measure popularized by Warren Buffett. This ratio currently stands at around 244%, meaning stocks are worth more than twice what the U.S. economy produces in a year. In the aftermath of the dot-com bubble, when this indicator reached as high as 190%, Buffett warned that approaching 200% meant investors were "playing with fire."

Analysts note a key distinction between the late 1990s and today: the dot-com craze was driven largely by companies with minimal actual earnings, whereas today's market leaders have substantial earnings. Nevertheless, the current market appears frothy despite the strong performance of companies like Nvidia and Alphabet. The CAPE ratio serves as a tool for gauging general returns over time rather than predicting an imminent crash. With the ratio above 40, historical data suggests that stock market underperformance is probable over the next decade.

Long-term data indicates that remaining invested continues to yield rewards. An investment of $1,000 in an exchange-traded fund tracking the S&P 500 at the dot-com peak on March 24, 2000, would be worth more than $5,000 today before accounting for dividends.