Background
During a discussion about investment systems, someone asked: What is the role of stop loss? This dialogue starts from the essence of stop loss and gradually explores its relationship with system survival.
Key Concepts
- Scope of this series: Trend investing — not short-term trading or value investing
- Stop Loss: Limiting the damage a single mistake does to the overall system, not avoiding losses
- Single-Trade Risk: The proportion of a single loss relative to total capital
- System Stability: The system’s ability to continue operating
1. The Role of Stop Loss
Q: What role does stop loss play in an investment system?
Response: Stop loss is not about avoiding losses, but about limiting the damage a single mistake does to the overall system.
2. Why Must We Assume We’ll Make Wrong Judgments?
Q: Why must a system assume it will make wrong judgments?
Response: Because uncertainty is the normal state of the market, not an exception.
3. Is Stricter Stop Loss Always Better?
Q: Is stricter stop loss always better?
Response: A stop loss that’s too tight treats normal fluctuations as mistakes. A stop loss that’s too loose amplifies the consequences of a single mistake.
4. The Core of Stop Loss
Q: What is the core of stop loss?
Response: Not the price level, but the proportion of a single loss relative to total capital.
5. What Happens Without Stop Loss?
Q: What happens if a system doesn’t set stop loss?
Response: The system may appear effective most of the time, but will fail in one extreme situation and terminate all historical gains.
6. What Does Stop Loss Truly Protect?
Q: So what does stop loss truly protect?
Response: Not a particular trade, but the qualification for the system to continue operating.