By Mari Hansen 
When something out of the ordinary emerges beneath all the commotion, a certain kind of silence descends upon the financial markets. It’s just a number that stealthily crosses a threshold it’s only crossed once in living memory, not a crash or a headline. The Shiller CAPE ratio, which recently surpassed 40 on the S&P 500, is responsible for the recent breach of that threshold. It hasn’t done that since 1999, and the results weren’t good.
To be fair, the frantic, coffee-stained chaos of the dot-com era doesn’t resemble the atmosphere on Wall Street as 2026 approaches. The language is more measured, and the offices are quieter. Fund managers carefully discuss “AI infrastructure” and “productivity cycles” rather than page views and eyeballs.
| Detail | Information |
|---|---|
| Index Name | S&P 500 (Standard & Poor’s 500) |
| Index Type | Market-capitalization-weighted stock index |
| Managed By | S&P Dow Jones Indices |
| Components | 500 largest U.S. publicly traded companies |
| Current Signal | Shiller CAPE Ratio crossed 40 threshold |
| Last Time CAPE > 40 | 1999 dot-com bubble peak |
| S&P 500 Return (2023) | +26% |
| S&P 500 Return (2024) | +23% |
| Forward P/E Ratio | ~23x (25-year average: 16.3x) |
| Post-1999 CAPE Decline | S&P 500 fell ~37% over two years |
| Reference Website | S&P Dow Jones Indices |
Beneath the polished language, however, there’s a persistent feeling that investors are once again placing large bets on a future that might be coming more slowly than the stock prices indicate.
With gains of 26% in 2023 and 23% in 2024, the S&P 500 concluded two remarkable years that were primarily fueled by excitement surrounding artificial intelligence and three interest rate cuts by the Federal Reserve since 2024. Similar to how Cisco used to be, NVIDIA became somewhat of a cultural icon. The claim that AI is truly unique and will transform global productivity in the same way that the internet did in the 1990s is made with fervor and repetition.
That argument might be true. However, given how that specific story ended, investors should probably be concerned rather than reassured by the 1990s comparison.
Formally known as the Cyclically Adjusted Price-to-Earnings ratio, the Shiller CAPE ratio compares stock prices to ten-year averages of inflation-adjusted earnings. It provides a longer-term picture of whether markets are stretched or fairly priced by reducing the short-term noise. Investors are being informed at 40 that stocks are costly by nearly all historical standards.
The picture is further enhanced by the forward price-to-earnings ratio, which is close to 23x and significantly higher than the 25-year average of 16.3x. When taken as a whole, these figures show that the market is priced for almost perfect results rather than just good ones.
It’s difficult to ignore the quiet confidence that permeates any major financial district these days, the kind that develops after three years of success. It feels well-deserved. And it is, in certain respects. The companies driving this rally are more than just speculative shells.
The economy hasn’t entered a recession, corporate profits are real, and AI revenue is starting to materialize. These are significant variations from 1999. However, the underlying quality of the businesses being valued is not always taken into consideration by the mechanics of overvaluation.
Here, historical data doesn’t provide much solace. In previous cycles, the market has eventually retreated—sometimes by 20%, sometimes by much more—after the CAPE ratio surpassed 30. The S&P 500 returned about 37% of its value over the following two years after the ratio surpassed 40 in late 1999. The market reported returns of more than 20% per year for five years in a row between 1995 and 1999.
At the time, investors thought the outdated valuation guidelines were no longer relevant. It turned out to be one of the most costly presumptions in market history.
Whether 2026 will see a correction, a crash, or just a protracted period of sideways growth as earnings gradually catch up to prices is still up in the air. The AI buildout is actually accelerating in ways that could maintain high earnings for a while, and markets can remain pricey for years. However, there is very little opportunity for disappointment in a market that is priced for perfection.
As the early weeks of 2026 already seem to be suggesting, a single major technology company’s earnings miss, an unexpected change in Fed policy, or a geopolitical shock could all be sufficient to quickly alter the mood, with the S&P down about 4% since January.
The realization that the risk-reward equation has changed is the signal that investors who are heavily invested in mega-cap technology stocks should pay attention to, rather than the forecast of a crash. It is not pessimistic to take a portion of the profits from the companies that have fueled this rally and rotate them into dividend-paying stocks, defensive industries, or foreign stocks.
Most investors only wish they had followed this type of portfolio hygiene the last time the CAPE exceeded 40. In particular, retirees face an asymmetric situation where the potential harm of a multi-year drawdown at the wrong time in their financial lives outweighs the benefits of holding on.
History does not ensure that it will happen again. However, it does have a tendency to reward those who pay attention to its patterns, particularly when the signal is so loud and uncommon.