📖Jeremy Grantham

Know Your Limits

🌱 Beginner★★★★★

Stay within your circle of competence.

💬

The most successful investors stay within their circle of competence. Know what you understand well and resist the temptation to venture outside it.

— GMO Quarterly Letters,2017

🏠 Everyday Analogy

A process is like a pilot checklist: discipline prevents simple mistakes when pressure rises and keeps outcomes more repeatable.

📖 Core Interpretation

Jeremy Grantham advocates a repeatable process: define criteria, execute consistently, and review decisions against evidence. Process quality drives outcome consistency.
💎 Key Insight:Self-awareness about knowledge limits prevents costly mistakes.

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❓ Why It Matters

Without process, there is no reliable feedback loop. Structured execution and review improve decision quality over time.

🎯 How to Practice

Run a decision loop of research, thesis, execution, and post-mortem; document assumptions and update playbooks with evidence, not hindsight bias.

⚠️ Common Pitfalls

Having opinions without execution criteria
Reviewing outcomes but not decisions
Abandoning rules during volatility spikes

📚 Case Studies

1
Avoiding the Tech Bubble (1999)
Grantham underweighted expensive tech stocks despite client pressure as valuations broke from historical norms.
✨ Outcome:Clients lagged during the final bubble phase but were largely spared the 2000–2002 crash, preserving capital and careers for patient managers.
2
Early Exit Before Global Financial Crisis (2007)
GMO reduced risk in equities and housing-related assets as Grantham warned of a major credit and housing bubble.
✨ Outcome:Some clients left due to short-term underperformance, but remaining investors suffered far smaller losses in 2008–2009, validating a risk-first approach.

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