Circle of Competence
Only do what you truly understand; knowing boundaries is more important than expanding them
📌 Concept Explanation
Circle of Competence = The range of companies whose future cash flows you can genuinely understand.
You’re a chef; Sichuan cuisine is your specialty—when customers order Sichuan dishes, you’re confident. But someone asks you to make French food; you’ve watched a few videos but never actually done it—if you take the order anyway, you’ll probably fail. Knowing you only cook Sichuan is far wiser than pretending you can do everything.
💡 Core Understanding
1. Knowing your boundaries is more important than expanding them; size isn’t important—knowing where the boundary lies is.
Duan said “I understand very few businesses. The difference between me and many people is that I admit I understand very few, so it becomes simple”—admitting what you don’t understand is the most important part of circle of competence.
2. Circle of competence is the true meaning of margin of safety; businesses within your circle are often easier to understand.
Margin of safety should actually refer to circle of competence, not merely price. For businesses within your circle of competence, you often understand them well yourself; what’s uncertain for others is often certain for you.
3. Don’t easily expand your circle of competence—understanding a business often takes many years.
Circle of competence is hard to expand; reading books alone won’t do it.
4. Most people who lose money in the stock market long-term belong to those who don’t know how big their circle of competence is.
Concentrated investing is the natural result of circle of competence—there are few companies you can understand within your circle, so concentrate rather than diversify.
💬 Original Quotes
“Knowing how large your circle of competence is is far more important than how large it actually is!” (Source: Investment Logic Chapter, Section 2.2)
“Those who lose money long-term in the stock market mostly belong to those who don’t know how big their circle of competence is.” (Source: Investment Logic Chapter, Section 3.3, 2012-07-28)
“Don’t easily try to ‘expand’ your circle of competence. Understanding a business often takes many years. Don’t jump into unfamiliar fields or places just because you’ve seen one or two concepts, or you’ll eventually trip up.” (Source: Investment Logic Chapter, Section 3.3, 2012-04-06)
“Actually, expanding circle of competence is difficult—at least reading books won’t do it. But reading more books can tell you how big your circle of competence is.” (Source: Investment Logic Chapter, Section 3.3, 2012-07-16)
“I understand very few businesses. The difference between me and many people is that I admit I understand very few, so it becomes simple.” (Source: Investment Logic Chapter, 2018-08-10)
“Size isn’t important—knowing where the boundary lies is important.” (Source: Investment Logic Chapter, 2013-10-20)
⚠️ Common Misconceptions
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❌ “The bigger the circle of competence, the better—keep working to expand it” — “Expanding your circle of competence may not be wise,” “For most capable investors, there are actually enough opportunities within their own circle of competence.” Circle of competence is hard to expand; reading books alone won’t do it.
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❌ “Margin of safety means buying cheaply enough; discounted price equals margin of safety” — “Margin of safety should actually refer to circle of competence, not merely price.” Within your circle of competence, your judgment of the enterprise itself is the greatest margin of safety.
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❌ “Learning from Buffett means learning which stocks he buys, imitating his trades” — “The most important thing people can learn from Buffett—and can learn—is what he doesn’t do! Most people learn the opposite: what he does, which is impossible to learn because everyone’s circle of competence differs.”
🔗 Related Nodes
Upstream Concepts (prerequisites for understanding this concept): Buying Stocks Means Buying Companies · Discounted Future Cash Flows
Downstream Concepts (conclusions derived from this): Business Model · Margin of Safety · Concentrated Investing · Stop Doing List · Macro and Markets · Understanding Financial Statements · Golf and Investing
Related Company Cases NetEase (Duan judged gaming market far exceeded expectations due to deep experience in gaming industry) · Apple
能力圈
只做自己真正懂的事，知道边界比扩大边界更重要
📌 概念解析
能力圈 = 你真正能看懂其未来现金流的那些企业的范围。
你是一个厨师，做川菜是你的拿手绝活，客人点川菜你心里有底。但有人让你做法餐，你虽然看过几个视频，却从没真正做过——这时候硬接单，大概率会翻车。知道自己只会川菜，比假装自己什么都会，要聪明得多。
💡 核心理解
1. 知道边界比扩大边界更重要，大小不重要，知道边界在哪儿才重要。
段永平说”我懂的生意非常少，和很多人的差别在于我承认我懂的少，所以就变简单了”——承认自己不懂，是能力圈最重要的部分。
2. 能力圈是安全边际的真正含义，在能力圈内的生意往往容易看懂。
margin of safety 实际上应该指的是能力圈而不仅仅是价格。在自己能力圈内的生意，自己往往容易懂得多，对别人的不确定性往往对自己是很确定的。
3. 不要轻易扩大能力圈，搞懂一个生意往往需要很多年。
能力圈很难扩大，靠读书也不行。
4. 股市上长期亏钱的大多属于不知道自己能力圈有多大的人。
集中投资是能力圈的自然结果——能力圈内能看懂的公司本来就很少，所以要集中，不要分散。
💬 原文金句
“知道自己的能力圈有多大往往比自己能力圈有多大要重要的多！“（来源：投资逻辑篇·第二章第2节）
“股市上那些长期亏錢的大多属于不知道自己能力圈有多大的人。“（来源：投资逻辑篇·第三章第3节，2012-07-28）
“不要轻易去’扩大’自己的能力圈。搞懂一个生意往往是需要很多年的，不要因为看到一两个概念就轻易跳进自己不熟悉的领域或地方，不然早晚会栽的。“（来源：投资逻辑篇·第三章第3节，2012-04-06）
“其实能力圈很难扩大的，至少靠读书不行。不过，多读点书能告诉自己能力圈有多大。“（来源：投资逻辑篇·第三章第3节，2012-07-16）
“我懂的生意非常少，和很多人的差别在于我承认我懂的少，所以就变简单了。“（来源：投资逻辑篇，2018-08-10）
“大小不重要，知道边界在哪儿才重要。“（来源：投资逻辑篇，2013-10-20）
⚠️ 常见误区
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❌ “能力圈越大越好，要不断努力扩大自己的能力圈” — “扩大自己的能力圈未必是明智的”，“对大多数有能力投资的人而言，自己的能力圈里能做的事情实际上往往是足够多的”。能力圈很难扩大，靠读书也不行。
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❌ “安全边际就是买得足够便宜，价格打折就是安全边际” — “margin of safety 实际上应该指的是能力圈而不仅仅是价格”。在能力圈内，你对企业的判断本身就是最大的安全边际。
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❌ “学巴菲特就是学他买了什么股票，模仿他的操作” — “学巴菲特最重要和人们能够学的东西其实是他不做什么！绝大多数人学的是相反的东西，就是他在做什么，那是没办法学的，因为每个人的能力圈不同。”
🔗 关联节点
上游概念（理解这个概念的前提）： 买股票就是买公司 · 未来现金流折现
下游概念（由此推导出的结论）： 生意模式 · 安全边际 · 集中投资 · Stop Doing List · 宏观与市场 · 财报的理解 · Golf与投资