📖Joel Greenblatt
Review Your Investment Thesis
Regularly challenge your original investment thesis.
Regularly review whether your original reasons for owning a stock still hold. If the facts change, change your mind. Holding a broken thesis is the costliest mistake.
🏠 Everyday Analogy
📖 Core Interpretation
Joel Greenblatt frames investing as a compounding game. Time amplifies quality and discipline, while unnecessary activity often destroys long-horizon returns.
💎 Key Insight：Adapting to new facts prevents holding broken investments.
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❓ Why It Matters
Short-term noise often forces investors out before value is realized. Long-term discipline increases the odds that fundamentals, not emotions, drive outcomes.
🎯 How to Practice
Extend research and review horizon, reduce unnecessary turnover, and adjust only when intrinsic value, risk, or opportunity cost materially changes.
⚠️ Common Pitfalls
Calling it long term while never reviewing thesis
Overtrading and damaging compounding
Ignoring opportunity cost and alternatives
📚 Case Studies
1
Avoiding Complex Tech Mania (2000)
During the dot-com bubble, Greenblatt emphasized avoiding hard-to-value tech companies with no profits and unclear models.
✨ Outcome：Investors who stayed with simple, profitable businesses avoided the crash and outperformed over the next decade.
2
Apple Post-Dot-Com Bust (2000)
After the tech bubble burst, Apple traded at a low earnings yield despite strong product pipeline and improving profitability.
✨ Outcome：Investors focusing on high earnings yield and durable business saw significant multiple expansion and outsized returns over the next decade.
📌 Save this principle as your rule
One click to drop it into your personal rule library — every future trade will be scored against it.
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