Mr. Market — 1987

Writing his 1987 shareholder letter not long after the October stock market crash known as Black Monday, Warren Buffett devoted an extended passage to reminding Berkshire's shareholders of one of the most important ideas he'd learned from his teacher Benjamin Graham: the allegory of Mr. Market.

The Concept

Buffett opened the passage by explaining how he and Charlie Munger actually approach buying a stock: as if buying into a private business outright, weighing its economic prospects, the people running it, and the price being asked, with no particular time or price in mind for eventually selling. An active market for the shares helps, since it occasionally hands you a great price, but it isn't essential — Buffett said a long halt in trading wouldn't bother him any more than the absence of daily price quotes on a wholly private company he owned, since the business's own results, not its quotes, would decide the outcome either way. He then retold Graham's Mr. Market allegory in his own words for shareholders: imagine the market as an obliging partner who shows up every day offering to buy your stake or sell you his, and whose price swings wildly with his mood — euphoric and demanding a high price one day, despondent and desperate to sell cheap the next — while never requiring you to trade with him at all. Buffett's warning was that Mr. Market is useful for his pocketbook, not his judgment, and that an investor who can't value a business better than Mr. Market's mood of the day doesn't belong in the game at all. He closed the section by tying it back to another of Graham's ideas — that in the short run the market behaves like a popularity contest, but over the long run it eventually weighs a business by its actual results — and by rejecting the idea that a position should ever be sold simply because it has gone up or been held a long time — the only real questions, he wrote, are whether the business's economics remain satisfactory, whether management is still competent and honest, and whether the market has pushed the price well past what the business is actually worth.

Buffett's own summary of the lesson, aimed squarely at the market panic his shareholders had just lived through, was blunt:

"Mr. Market is there to serve you, not to guide you."

The practical instruction that follows is simple to state and hard to practice: an investor who has done the work of estimating a business's actual worth should use Mr. Market's wild price swings as opportunities to act — buying when his offer is absurdly low, selling when it's absurdly high, and otherwise ignoring him — rather than treating his daily quote as a verdict to be obeyed.

Why It Matters

The 1987 letter's timing made the lesson unusually vivid: shareholders reading it had just watched paper values fall dramatically over a matter of days, with no comparable change in the actual businesses those shares represented. Buffett's argument was that this kind of gap between price and value is exactly when the Mr. Market framework earns its keep — a sharp, sentiment-driven price drop is either irrelevant to a business's real worth or, better yet, an invitation to buy more of it cheaply, not a signal that something has gone wrong.

This idea remains one of the most practically useful mental models in investing precisely because market volatility hasn't gone away. Every downturn resurfaces the same test: does a falling price reflect a genuine deterioration in a business's prospects, or is it just Mr. Market having one of his moods? Investors who've done independent work estimating intrinsic value have a fixed reference point to answer that question; investors who haven't tend to let the price itself set their expectations, which is exactly the trap Graham's allegory was designed to help investors avoid.