The Stock Market Sounds an Alarm for the First Time in Nearly 27 Years. Here Is What History Says the S&P 500 Will Do Next.

Following nearly 27 years without a significant correction, the S&P 500 (^GSPC -1.47%) has surged 12% this year, buoyed by optimism surrounding artificial intelligence (AI). However, the rally has not been without challenges. Both the S&P 500 and Nasdaq Composite (^IXIC -2.78%) experienced sharp declines recently, as investors contend with persistent inflation, high bond yields, and concerns about the funding of the AI revolution.

There is another cause for caution: the CAPE ratio and Buffett indicator indicate the stock market is presently expensive. The CAPE ratio, popularized by economist Robert Shiller, compares the S&P 500's price to the average of 10 years of inflation-adjusted earnings, currently sitting at 41, nearly double its historic average of 17.8.

In the past 155 years of stock market data, the CAPE ratio exceeded 40 only during the dot-com bubble, peaking at 44 in December 1999. Additionally, the Buffett indicator, which compares the total market capitalization of U.S. stocks to the country's annual GDP, currently stands at 237%. This suggests the market is valued at $2.37 for every $1 of annual U.S. economic output, potentially signaling stocks are overvalued.

While this might appear alarming, the current valuation differences stem from today's large, profitable companies like Microsoft, Alphabet, Amazon, and Nvidia, which contrast with the speculative internet firms of the dot-com era. The metrics may signal weaker future returns, but they do not definitively forecast a crash. Instead, investors could reassess risk by trimming overexposure to AI stocks and diversifying into established businesses with strong balance sheets, durable competitive advantages, and consistent cash flow.

The focus should be on resilient companies capable of generating shareholder value through any upcoming economic cycle.