Rationality and Exuberance

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Predicting what’s next has been a fool’s game, and it continues to be. The S&P 500 was up 26% in 2023 and 25% in 2024, for the best two-year stretch since 1997-98. That brings us to 2025. What lies ahead? Rationality, Optimism, exuberance, disappointment, correction, and more frequent and intense volatility—with uncertainty about the timing, extent, and outcome. Is enthusiasm for new technology creating a bubble, and will the bubble burst? Optimism has prevailed in the markets since late 2022, generating above-average valuations and astonishing returns for some (primarily AI-related) equities. Stocks in most industrial groups sell at high multiples, but enthusiasm for artificial intelligence and the persistence of the Magnificent 7 drive most market expectations. There is the implicit presumption that the top seven companies will continue to be successful and that the “new thing” (artificial intelligence) will drive valuations even higher. However, stocks may sit still for the next 10 years as earnings rise and multiples return to earth. Another possibility is that the multiple correction is compressed into a year or two, implying a significant decline in stock prices. Be aware of Mr. Market’s irrational behavior. It’s not going to be a smooth pathway forward; there will be great investment opportunities, as there are in any market, but overall, it’s a high starting point. It’s time to be neutral.

Uncertainty and Irrationality

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Clear and coherent markets, free from political agenda, bad compromises, and ineffective regulation is almost nonexistent. The consequences are usually pyrotechnic. It is not as if the world hadn’t provided ample warnings about the risks associated with irresponsible finance. History has centuries worth of such examples, but even looking at recent events over the last 25 years is illuminating.

In spite of Alan Greenspan acknowledging the “irrational exuberance” of the markets in 1996, stock market valuations continued to rise. The warning signs of unstable economies were believed to be localized and the broader markets decoupled from this turbulence. This was naïve thinking then and outright irresponsible now.

The idea that markets are uncertain, and consistent prediction is essentially impossible, is not new. John Maynard Keynes published a book on probability and uncertainty in 1921, with this concept of uncertain and irrational markets forming the basis of his general theory of financial markets. So, years before the stock market crash of 1929, and almost every 10 to 15 years afterward, the cycle of financial crashes and panics was predicted by a well-publicized thinker, and then, as is typical, ignored. The lesson is simple, and Keynes laid it out 100 years ago: markets seem rational but only during periods of stability. Markets are uncertain. Predictive models work most of the time, and that is their fundamental flaw. They will fail. Investment models that account for uncertainty and failure succeed in the long term.