Buffett’s rule is that you do not need to value every business in the world. You need to value a few of them well. The grid below is one stylized way of looking at the investable universe. Most cells are gray — businesses you cannot value with any confidence. A handful are tan: the ones inside your circle. The discipline is not about making the circle bigger. It is about knowing exactly where its edge is.
Chart 1 · The universe
Tan = businesses you can value with confidence. Light tan = adjacent businesses you could learn to value with real work. Gray = businesses you cannot value, and probably never will, and that is fine. The point of the chart is not the exact ratios. It is that most of the universe is gray, even for a sophisticated investor.
The chart is intentionally humbling. Even a sophisticated value investor’s circle is small relative to the universe of investable businesses. The job is not to grow the circle to cover everything; doing so would make every position diluted and shallow. The job is to grow the edge precision: to know, for any new name, within ten minutes of reading whether it is tan, light tan, or gray for you. The wrong move is to color a gray cell tan because the price is exciting.
Chart 2 · The three-question test
If you can answer all three, the cell is at least light tan. If two are easy and one is unsure, it is adjacent — potentially in your circle with work. If you cannot get started on any of them, the cell is gray. Skip it, no matter how cheap it looks.
Question 01
How does this business make money, in one sentence?
Pass looks likeOne sentence that names the customer, the product, and the unit economics. Not “they sell software” but “they sell mid-market HR payroll software at $15 per employee per month, and the gross margin on each new seat is 85% because the COGS is mostly storage.”
Fail looks likeVague verbs (“they provide services”), industry jargon you cannot decode, or any sentence that contains the word “ecosystem.”
Question 02
Who are three competitors, and what does this business do that they do not?
Pass looks likeThree specific named competitors. One non-trivial structural difference (a moat candidate): scale, switching cost, network effect, regulatory protection, brand-as-habit. Not “they are higher quality”; something you could test in the next earnings report.
Fail looks likeVague competition (“the whole industry”), or a differentiation claim that sounds good but you cannot operationalize.
Question 03
What substitute or technology could obsolete this in ten years?
Pass looks likeA specific named threat (“commodity chemicals from China”, “an AI tool that replaces the entry-level analyst”, “a regulatory change that opens the network”), and an honest assessment of its adoption curve and probability.
Fail looks like“Nothing could threaten this” (almost always wrong), or a vague hand-wave that you cannot picture happening.
Failing the test is not a problem. Passing on a business you cannot evaluate is a strictly better outcome than buying one you cannot evaluate. Most of the visible universe is gray; that is fine. The visible universe is wider than the time available to learn it, so trying to cover everything is structurally impossible. Better to know five businesses well than to know a hundred in passing.