📖Philip Fisher
Review Your Original Thesis
The original investment thesis should guide sell decisions.
Periodically review whether your original reasons for buying still hold. If they do, hold; if they don't, sell. The thesis, not the price, should drive the decision.
🏠 Everyday Analogy
📖 Core Interpretation
In Review Your Original Thesis, Philip Fisher focuses on the gap between price and value. Returns come from paying less than what a business is worth, not from guessing short-term market moves.
💎 Key Insight：Thesis-driven selling prevents emotional mistakes.
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❓ Why It Matters
Ignoring valuation turns even good companies into poor investments. Overpaying compresses future returns and leaves little margin when assumptions are wrong.
🎯 How to Practice
Estimate intrinsic value with conservative assumptions, set clear buy ranges, and act only when price offers a meaningful discount with acceptable downside.
⚠️ Common Pitfalls
Confusing a low price with true cheapness
Using one metric without business context
Overly optimistic assumptions that erase margin of safety
📚 Case Studies
1
Motorola Growth Insight (1956)
Applied scuttlebutt by interviewing engineers, suppliers, and competitors to assess Motorola’s transistor leadership and R&D culture.
✨ Outcome：Built a large, long-term position; investment compounded for decades as Motorola became a dominant electronics and semiconductor player.
2
Texas Instruments Evaluation (1963)
Used industry contacts to compare TI’s management, innovation pace, and customer reputation with Motorola’s in semiconductors.
✨ Outcome：Chose to limit TI exposure and emphasize Motorola, reinforcing Fisher’s focus on qualitative advantages identified through scuttlebutt.
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