Jeremy Grantham: Brilliant Bubble Spotter or the World's Most Expensive Bear?

Jeremy Grantham has been right about bubbles. So why has following him often been so costly?

Jeremy Grantham occupies a unique place in investing.

He is one of the few investors who correctly identified the Japanese bubble, the dot-com bubble and the US housing bubble before they burst. That track record deserves enormous respect.

But there is an equally important question investors rarely ask:

Has Jeremy Grantham actually been a good guide to making money?

Spotting a bubble and generating superior investment returns are not the same thing.

In fact, they can be complete opposites.

The Difference Between being Right and being Useful

Suppose someone predicts every year that London will eventually have another major flood. Eventually they will be correct. That does not mean buying a boat every January is a sensible investment strategy.

This is the central weakness of Jeremy Grantham's investment philosophy. Valuation tells us a great deal about the next decade. It often tells us remarkably little about the next twelve months.

Markets can become expensive. Then very expensive. Then absurdly expensive. And finally even more expensive.

The investor who exits too early receives no prize for intellectual correctness.

Valuation is Not Timing

One of the most persistent myths in investing is that expensive markets must soon fall.

History repeatedly demonstrates otherwise.

The US market remained expensive throughout much of the 1990s. Many technology companies continued rising long after traditional valuation measures suggested they should.

Today the same criticism is made of artificial intelligence companies. Some undoubtedly are overvalued. Others are producing extraordinary earnings growth that continually changes what constitutes "fair value."

Valuation is important.

Timing is everything.

Confusing the two has destroyed many fortunes.

Today's Technology Companies are Not Pets.com

One mistake many permanent bears make is assuming all bubbles are alike.

They are not.

The dot-com era contained thousands of businesses with little revenue and no sustainable profits.

Today's market leaders include companies such as Microsoft, Nvidia, Alphabet, Meta and Amazon.

These businesses generate tens of billions of dollars in annual free cash flow.

They dominate global markets. They possess enormous pricing power.

They own infrastructure that competitors struggle to replicate.

They may occasionally become overpriced.

That does not mean they are worthless.

Nor does it mean they resemble the speculative companies of 1999.

When Every Outcome Confirms your Thesis

One feature common to many permanent bears is that every market outcome appears to validate their worldview.

If markets rise, the bubble is getting bigger.

If markets fall, the crash has begun.

If valuations widen, irrational exuberance.

If valuations narrow, the reckoning is finally here.

This creates an unfalsifiable investment philosophy.

No evidence can ever disprove it.

Science progresses by testing ideas that can be wrong.

Investment strategies should do the same.

Why Might Jeremy Grantham Always Expect Disaster?

It is impossible, and inappropriate, to diagnose anyone's mental health from public behaviour.

However, behavioural finance provides several plausible explanations for why even brilliant investors can become permanently bearish.

1. Identity becomes difficult to escape

Jeremy Grantham built his reputation by spotting major bubbles before others.

That success became part of his professional identity.

When investors become known for one thing, changing course becomes psychologically difficult.

If everyone calls you "the bubble expert," optimism almost feels like abandoning your life's work.

2. Availability bias

People naturally expect future events to resemble the most memorable events from their past.

If your greatest career successes came from identifying spectacular crashes, every period of market optimism begins to resemble previous bubbles.

History becomes a template through which every new market is viewed.

3. Confirmation bias

Once an investor develops a strong bearish framework, evidence supporting that framework becomes easier to notice.

Evidence contradicting it becomes easier to dismiss. Every investor suffers from confirmation bias. The most successful continually search for information proving themselves wrong.

4. Reputation creates asymmetric incentives

There is surprisingly little career risk in repeatedly predicting disaster. If the crash never arrives, people say you were early. If the crash finally comes, you become a prophet.

The reputational payoff is asymmetric. Permanent bears rarely lose their audience.

The Opportunity Cost of Permanent Pessimism

Missing one major bull market can permanently reduce lifetime wealth.

Consider the mathematics.

A portfolio compounding at 12% annually doubles roughly every six years.

Miss one decade waiting for "the inevitable crash" and recovering that lost compounding becomes extraordinarily difficult.

Opportunity cost is invisible.

But it is one of investing's greatest risks.

What Private Investors Should Actually Learn from Jeremy Grantham

Jeremy Grantham should not be ignored. Nor should he be followed blindly.

His greatest contribution is reminding investors that price matters. His greatest weakness is suggesting that expensive markets must soon correct. Those are very different propositions.

Successful investors recognise overvaluation. But they also recognise momentum.

They understand earnings growth. They appreciate technological change. And above all, they avoid allowing fear to dominate long-term decision making.

Markets frequently become irrational. Businesses continue creating wealth anyway.

Conclusion

Jeremy Grantham is one of the greatest students of financial bubbles. He deserves enormous credit for that achievement. But identifying excess is only half of investing.

The other half is understanding how long excess can persist, how innovation changes valuations, and how costly permanent pessimism can become. The danger is not listening to Jeremy Grantham. The danger is allowing his worldview to stop you participating in decades of wealth creation.

In investing, being early is often indistinguishable from being wrong.

Frequently asked questions

Is Jeremy Grantham a perma-bear?

Jeremy Grantham is widely regarded as one of the world's best-known long-term bearish investors because he has repeatedly warned about asset bubbles and elevated market valuations over several decades.

Has Jeremy Grantham ever been right?

Yes. He correctly warned about the Japanese asset bubble, the dot-com bubble and the US housing bubble before they burst. Those calls established his reputation.

Has Jeremy Grantham been wrong?

Like many macro forecasters, he has often identified valuation extremes years before markets eventually corrected. For investors who exited too early, the opportunity cost was substantial.

Why do some investors become permanent bears?

Behavioural finance suggests several possible explanations, including identity reinforcement, confirmation bias, availability bias and reputational incentives. These are common cognitive tendencies rather than indicators of psychiatric illness.

Does valuation predict stock market returns?

Valuation is a useful predictor of long-term returns. It is a poor predictor of short-term market movements. Markets can remain expensive for many years.

Should investors sell because the market looks expensive?

Not necessarily. Investment decisions should consider earnings growth, business quality, diversification, liquidity needs, tax considerations and investment horizon rather than valuation alone.

This article is for information and education only. It is not a personal recommendation and does not take account of your individual circumstances. Investing puts your capital at risk and you may get back less than you invest. Past performance is not a reliable indicator of future results. Where you need guidance tailored to your situation, consider a suitably regulated professional.

Want a repeatable system for building your own portfolio? The Great Investments Programme applies institutional-grade quantitative methods to self-directed investing. Learn more at campaignforamillion.com and alpeshpatel.com/shares.

Alpesh Patel OBE www.campaignforamillion.com