Sunk Cost
Money already spent shouldn’t influence your decisions today.
📌 Concept Analysis
Sunk cost = Costs that have already been incurred and cannot be recovered; they should not become a reason to continue investing.
You buy a movie ticket, go in, and discover the film is terrible. Will you sit through it just because “the ticket money’s already spent”? The rational approach: the ticket money is sunk—whether you leave or stay, it won’t come back. Staying there is only wasting your time. Investing is the same—the purchase price is sunk cost; it shouldn’t affect your judgment today on “whether this stock is worth continuing to hold.”
💡 Core Understanding
1. Sunk cost is the most common psychological trap in investing, directly causing “holding onto losses longer and longer.”
After most people get trapped in losing positions, they wait for “break-even” rather than calmly comparing whether “continuing to hold” or “switching to other targets” offers greater opportunity. This is sunk cost at work—the purchase price becomes a psychological anchor preventing rational selling logic judgment. Duan Yongping says over 95% of people struggle with this most of the time.
2. Each day’s closing price is your opportunity cost; not selling equals buying again today.
This is the most powerful perspective for understanding sunk cost: you hold this stock today not because of what you originally paid for it, but because today you choose to continue holding it rather than switching to something better. This is one with opportunity cost—your purchase price has nothing to do with today’s decision; today’s decision relates only to “this stock’s future value.”
3. Truly understanding sunk cost enables you to “forget the purchase price and view how much the company is worth with an ordinary mind.”
Duan Yongping says this is the hardest hurdle. When you discover you bought wrong, sell immediately—don’t comfort yourself with “waiting for break-even.” The core of mistakes and correction lies here: the cost of admitting an error is far smaller than the cost of continuing to hold a wrong decision. The spirit of Stop Doing List also lies here: once you discover it’s a pit, stop digging.
🛠 How to Practice
Whenever facing a holding decision, ask yourself this question:
“If I had cash in hand today, would I buy this stock?”
If the answer is “no,” then the only reason you’re continuing to hold is sunk cost—you don’t want to admit a loss. At this point, the right approach is to sell, not wait.
Three signals that indicate you’ve fallen into the sunk cost trap:
- You say “I’ll sell when it bounces back” — this is sunk cost thinking
- You say “I’ve already lost so much; another drop doesn’t matter” — this is sunk cost thinking
- You say “I’m a long-term investor,” but your original buying logic has long since ceased to apply—this is also sunk cost thinking
❓ Selected Q&A
Q: Mr. Duan, I’d like to ask: Munger said “We don’t sell a company simply because it’s in trouble,” while Buffett said “If it’s a hole, stop digging.” Can these two statements apply to the same company? I’m still conflicted by past sunk costs.
A: If it’s the right company, you shouldn’t sell it when it’s cheap. If it’s the wrong company, at least don’t buy more. If you feel the company you currently hold will collapse at some point in the foreseeable future, do you think you should: 1. Add to your position because you lost money before and want to average down so you can recover costs when it rebounds? 2. Don’t buy but don’t sell either, hoping for a rebound opportunity to exit? 3. Forget what price you bought at and think with an ordinary mind about what this company is worth? …This last option is the hardest.
Source: Duan Yongping Investment Q&A (Investment Logic), 2013-04-08
⚠️ Common Misconceptions
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❌ “If you lose money, you must wait for break-even, otherwise the loss becomes real” — Correct view: Duan Yongping says there’s a financial term called sunk cost—if you truly understand it, you can resolve this question. A loss doesn’t “become real” at the moment of sale—it occurred the moment you bought wrong. (Source: Duan Yongping Investment Q&A (Investment Logic), 2013-12-28)
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❌ “Averaging down is a rational operation” — Correct view: If the company itself is wrong, averaging down is just digging yourself deeper in the same pit. What Munger calls “stop digging” addresses exactly this situation. (Source: Duan Yongping Investment Q&A (Investment Logic), 2012-06-26)
💬 Original Quotes
“There’s a term in finance called sunk cost. If you truly understand it, you can solve your problem. I believe over 95% of people will struggle with this most of the time.” (Source: Duan Yongping Investment Q&A (Investment Logic), 2013-12-28)
“Sunk cost refers to costs already incurred from past decisions that cannot be changed by any present or future decisions. The story describes spending new investment trying to rescue already-sunken money—the result is throwing good money after bad.” (Source: Duan Yongping Investment Q&A (Investment Logic), 2010-03-30)
“It makes me think of sunk cost. It also reminds me of what old Buffett said: if it’s a hole, stop digging. Just look at how many people are digging their own holes and you’ll understand.” (Source: Duan Yongping Investment Q&A (Investment Logic), 2012-06-26)
🔗 Related Nodes
Upstream Concepts (prerequisites for understanding this concept): Opportunity Cost · Ordinary Mind
Downstream Concepts (conclusions derived from this): Selling Logic · Mistakes and Correction · Stop Doing List
Related People Duan Yongping · Buffett · Munger
沉没成本
已经花出去的钱，不该影响你今天的决定
📌 概念解析
沉没成本 = 已经发生、无法收回的成本，不应该成为你继续投入的理由。
你买了一张电影票，进场后发现电影很烂。你会因为”票钱已经花了”而坚持看完吗？理性的做法是：票钱已经沉没了，不管你走不走都回不来了。继续坐在那里只是在浪费你的时间。投资也是一样——买入价格是沉没成本，它不应该影响你今天”这只股票值不值得继续持有”的判断。
💡 核心理解
1. 沉没成本是投资中最常见的心理陷阱，直接导致”越亏越拿”。
大多数人被套住之后，会守在那里等”解套”，而不是冷静比较”继续持有”和”换成其他标的”哪个机会更大。这就是沉没成本在作怪——买入价格成了心理锚点，让人无法做出理性的卖出逻辑判断。段永平说，95%以上的人大多数情况下会想不开。
2. 每天的收盘价就是你的机会成本，没有卖就等于今天重新买了一次。
这是理解沉没成本最有力的视角：你今天持有这只股票，不是因为你当初花了多少钱买的，而是因为你今天选择继续持有它，而不是换成其他更好的标的。这和机会成本是一体的——你的买入价格与今天的决策无关，今天的决策只和”这只股票未来的价值”有关。
3. 真正懂了沉没成本，就能做到”忘掉买入价，平常心看公司值多少钱”。
段永平说，这是最难的一关。发现买错了，要马上卖，而不是用”等解套”来安慰自己。错误与纠错的核心就在这里——承认错误的成本，远小于继续持有错误决策的成本。Stop Doing List的精神也在于此：发现是坑，就停止挖。
🛠 如何实践
每次面对持仓决策时，问自己这个问题：
“如果我今天手里拿的是现金，我会买这只股票吗？”
如果答案是”不会”，那你继续持有的唯一理由就是沉没成本——你不想承认亏损。这时候正确的做法是卖出，而不是等待。
判断是否陷入沉没成本陷阱的三个信号：
- 你说”等涨回来再卖”——这是沉没成本思维
- 你说”已经亏了这么多，再跌也无所谓了”——这是沉没成本思维
- 你说”我是长期投资者”，但买入逻辑早已不成立——这也是沉没成本思维
❓ 精选问答
问：请教段先生，“我们不会仅仅因为企业处于困境就卖掉它”（芒格）和”如果是个坑就别再往下挖了”（巴菲特），这两句话会适用在同一个公司吗？我还在过去的沉没成本中矛盾着。
答：如果是对的企业，就不应该在便宜的时候卖掉。如果是错的公司，至少不要再买了。如果你觉得自己现在持有的公司在看得到的未来某一天会完蛋，你觉得是应该：1. 加码，因为前面买的亏了，要摊低成本等他反弹时卖掉补回成本？2. 不买但也不卖，希望能有个反弹的机会卖掉？3. 忘掉自己什么价买的，平常心去想这个公司值多少钱？……这个最难。
来源：段永平投资问答录(投资逻辑篇)，2013-04-08
⚠️ 常见误区
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❌ “亏了就要等解套，不然就是真亏了” — 正解：段永平说，财务上有个名词叫沉没成本，如果你真懂了，你就能解答这个问题。亏损在卖出的那一刻并没有”变成真的”——它在你买错的那一刻就已经发生了。（来源：段永平投资问答录(投资逻辑篇)，2013-12-28）
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❌ “摊低成本是理性的操作” — 正解：如果公司本身是错的，摊低成本只是在一个坑里越挖越深。芒格说的”停止挖掘”，正是针对这种情况。（来源：段永平投资问答录(投资逻辑篇)，2012-06-26）
💬 原文金句
“财务上有个名词叫沉入成本，也有叫沉没成本的，如果你真懂了，你就能解答你的问题。我认为95%以上的人大多数情况下会想不开的。“（来源：段永平投资问答录(投资逻辑篇)，2013-12-28）
“沉入成本是指由于过去的决策已经发生了的，而不能由现在或将来的任何决策改变的成本。故事讲的就是为了去救已经沉没的钱又花了新的投资，结果是白花了。“（来源：段永平投资问答录(投资逻辑篇)，2010-03-30）
“想起沉入成本。还想起老巴说的，如果是个坑就别再往下挖了。看看有多少人在给自己挖坑就明白了。“（来源：段永平投资问答录(投资逻辑篇)，2012-06-26）
🔗 关联节点
下游概念（由此推导出的结论）： 卖出逻辑 · 错误与纠错 · Stop Doing List