The Trend is Your Friend, (Until It Isn't)

Jeremy Grantham: A Deep‑Value Pioneer Who Walked Away From the Dot‑Com Boom

When most investors were glued to their screens chasing the next tech headline, Jeremy Grantham - principal of Grantham, Mayo, Van Otterloo (GMO) and the manager of about $22 billion - made a headline‑making decision: he pulled his portfolio out of the Internet‑telecom‑tech craze of 1998 and 1999. That move was not a hasty retreat. It was the result of a long‑standing conviction that deep value outperforms in the long run, and that markets inevitably overreact to hype. Grantham’s reputation as a deep‑value investor is earned, not granted; his track record shows repeated wins over the market, but also a willingness to suffer significant short‑term losses when the evidence dictates otherwise.

In the months before the dot‑com crash, Grantham’s firm was facing pressure from pension funds and other institutional clients who wanted to stay invested in the soaring stocks that were dominating headlines. The pressure was not just a matter of client sentiment; it was a concrete financial threat. If the funds stayed, they could outgrow the firm’s assets and push GMO into a less favorable position relative to competitors. Grantham, however, stood by his value analysis. He calculated that the valuation multiples of tech stocks had deviated far beyond historic norms and that a pullback was inevitable. He chose to act, even though it meant losing 40% of his accounts - a staggering figure that illustrates the scale of the stakes involved.

The fallout was immediate. Investors who followed the mainstream narrative felt their portfolios underperform. Meanwhile, Grantham’s loyal base - those who understood the philosophy of value and had witnessed his previous successes - remained. Over time, the market confirmed his position: the bubble burst, valuations collapsed, and the firms that had stayed on the sidelines found themselves underweight when the market recovered. This episode underscores the paradox that investing can be a painful discipline; the price of sticking to fundamentals is often paid in the short term, but the reward shows up over the long horizon.

Beyond the immediate financial ramifications, Grantham’s decision revealed something about his character. He did not chase short‑term gains or try to align with the herd. He also did not give in to the “fear of missing out” that many fund managers felt when they saw colleagues reaping the bubble’s upside. Instead, he reinforced the principle that a disciplined, research‑based approach can win the long‑run battle against speculative excesses. For investors, the lesson is clear: the best times to invest are often the times when the market is tired of being overvalued.

Grantham’s story also demonstrates how a few key metrics can guide decisions. He relied heavily on valuation ratios - particularly the price‑earnings (P/E) multiple - and on historical averages. By comparing current P/Es to long‑term averages, he identified when a sector or the overall market was overextended. His early exit from the tech bubble, for example, was driven by an awareness that the S&P 500 had a P/E of 26, far above the 14‑year average of 14 and the 17‑year average of 17.5 that he had observed in prior cycles. In short, Grantham’s deep‑value philosophy rests on a simple but powerful rule: avoid assets whose valuations are too high relative to their long‑term norms.

Even after the crash, Grantham did not abandon his core belief. He continued to emphasize the importance of buying when prices are low and selling when they are high. In doing so, he positioned GMO to benefit from market cycles that eventually bring valuations back toward their historic equilibrium. Investors who adopt a similar lens can better navigate market swings, recognizing that short‑term volatility is normal and that disciplined adherence to fundamentals is essential for long‑term success.

The Trend‑Reversion Philosophy That Drives Grantham’s Investment Decisions

Grantham’s investment theory hinges on a single idea that is both elegant and grounded in historical evidence: asset classes tend to move back toward their long‑term averages. When a particular asset class - be it stocks, bonds, or commodities - is trading well above its historic trend, he steps back. When it falls well below, he steps forward. This approach turns market swings into opportunities rather than threats.

To illustrate, imagine the price of a stock index like the S&P 500. Over many decades, its P/E ratio has hovered around a certain range. When that ratio climbs to 30 or 35, it signals that the market is overvalued relative to its own history. Conversely, when it dips to 10 or 12, it indicates a relative undervaluation. Grantham applies this logic consistently across asset classes, recognizing that while individual sectors may exhibit idiosyncratic behavior, the overall trend of the market is a reliable guide. By waiting for the correction of extreme valuations, he can purchase assets at attractive prices and reap the upside when the market reverts.

Grantham’s research, often backed by his colleague Ben Inker, has documented 28 historic bubbles across multiple asset classes. Each bubble, defined as a 40‑year event where metrics exceeded two standard deviations from the mean, eventually reverted to the trend. There were no anomalies - a single case where a bubble persisted forever. This data-driven foundation provides a strong statistical case for the mean‑reversion principle.

Another element of his methodology is the long‑term horizon. He does not aim for short‑term gains; instead, he looks at decadal cycles. For instance, he once projected that the S&P 500’s P/E ratio would gravitate toward 17.5 over a ten‑year period, acknowledging that the current level of 26 might be unsustainable. He understood that a rapid adjustment could be painful, but a gradual, “graceful” correction would mean only modest negative returns over a decade. This long‑term perspective keeps investors focused on the big picture, reducing the temptation to react to daily market noise.

Grantham’s philosophy also addresses the productivity debate. While many argue that advances in technology or efficiency will automatically translate into higher profits, he cautions against assuming a direct link. He illustrates this with the example of corn production: if everyone receives a seed that doubles output, the price of corn will fall, eroding farmers’ profits unless they hold a competitive advantage. The lesson is that productivity gains spread across the market can actually dilute earnings, especially in competitive sectors. Investors should therefore not overvalue companies simply because they are involved in high‑growth industries without considering the broader market context.

Finally, Grantham’s trend‑reversion outlook extends to asset allocation. When capital‑spending cycles begin to wane, corporate earnings face pressure, and markets must adjust. Rather than predicting the exact timing, he emphasizes the structural realities: low interest rates and shrinking capital expenditures set the stage for a slowdown. By staying nimble and monitoring valuation metrics, investors can position themselves for the inevitable adjustments without making costly missteps.

Applying Grantham’s Lessons to Modern Markets

Grantham’s insights remain highly relevant today, especially as markets navigate the aftermath of rapid technology adoption, low interest rates, and the lingering effects of a global pandemic. Investors can translate his principles into actionable steps: focus on valuation, adopt a long‑term perspective, and be prepared to adjust positions as trends shift.

Valuation metrics, such as the P/E ratio, are still the cornerstone of a disciplined investment strategy. In 2001, Grantham warned that the S&P’s P/E of 26 - already above the historic average - was a red flag for a potential correction. Today, many markets still exhibit lofty multiples, especially in the technology and biotech sectors. By comparing current valuations to long‑term averages, investors can spot overextension early and avoid chasing inflated prices.

Grantham’s 2001 interview also touched on the concept of “bubbles” as 40‑year events that ultimately return to their trend. This perspective suggests that a market that appears exuberant today may still have several years of correction ahead. Rather than panic, investors should use this timeframe to build positions that will benefit when the market stabilizes. For instance, allocating a portion of a portfolio to value stocks or undervalued sectors can provide a cushion during a broader market slowdown.

In the debate with Professor Jeremy Siegel - an advocate of a pure buy‑and‑hold strategy - Grantham challenged the assumption that productivity gains automatically raise valuations. He argued that if a productivity improvement is shared across the market, it tends to compress prices rather than boost profits. For investors, this means that the hype surrounding new technologies should be weighed against realistic earnings impacts. A company may look attractive because of its tech stack, but if the market can achieve similar productivity through lower costs, the relative advantage may disappear.

Hussman Econometrics, a research firm, analyzed the S&P 500’s earnings growth over the past 40 years and found an average of 5.7% per year, including inflation. Even if future earnings grow at that rate, the long‑term price/earnings multiple is likely to hover around 15, which would represent a 13% decline in price relative to today’s levels over the next decade. This analysis underscores that current valuations are not sustainable if earnings remain at their historical pace. Investors who rely on short‑term gains should be wary of overreliance on momentum and instead consider whether the long‑term fundamentals justify current prices.

Practical applications of Grantham’s framework include:

• Regularly monitor key valuation ratios - P/E, P/B, and dividend yields - and compare them to 10‑year and 20‑year averages.
• Maintain a diversified portfolio that balances growth and value exposure, adjusting the mix when valuations diverge significantly from historic norms.
• Use macro‑economic signals - interest rates, capital‑spending trends, and productivity data - to anticipate market cycles and potential reversion points.
• Stay disciplined during periods of volatility; resist the urge to react to short‑term news if the long‑term outlook remains favorable.
• Rebalance periodically to ensure that the portfolio aligns with evolving valuation dynamics, rather than letting it drift into overvalued territory.

  By embracing a trend‑reversion mindset, investors can position themselves to benefit from market corrections while avoiding the pitfalls of chasing hype. Grantham’s career serves as a testament that a disciplined, valuation‑centric approach - paired with patience - can weather even the most turbulent market cycles.