Efficient Market Theory (EMT)

📍 Origin

Buffett's first sustained critique of EMT appeared in his 1984 Columbia University lecture ("The Superinvestors of Graham-and-Doddsville"), published as a 1984 essay and referenced in the 1988 Letter. The strongest version of the meeting-room critique was delivered at the 1998 Meeting — a direct, unambiguous comparison to medical schools teaching that germs don't cause disease.

🧠 The Core Argument

• The Premise: EMT posits that stock prices always reflect all available information, making it impossible to consistently achieve returns above the market through analysis or skill. Its logical corollary: skilled analysis is wasted effort.
• The Mechanism: If everyone believes EMT, the supply of skilled investors is suppressed. Fewer participants do the work of fundamental analysis. Mispricings accumulate — and persist longer — than they would in a world of active, rigorous investors. The doctrine thereby creates the very conditions it claims are impossible.
• The Conclusion: EMT is a theory that is partially true for widely-followed, liquid securities in ordinary market conditions, and disastrously wrong as a universal claim. A 43-year track record compiled across hundreds of securities is mathematically impossible if markets are perpetually efficient. The record doesn't prove markets are always wrong; it proves they are frequently wrong — and that disciplined investors can exploit those divergences.

📅 Chronological Evolution

• 1984 (Columbia Lecture / "Superinvestors"): The first systematic empirical rebuke. Buffett presents the records of nine Grahamite investors, all trained in the same analytical school, all with decades of above-market returns. Statistical impossibility if markets were efficient. He uses the coin-flipping analogy: if 225 million orangutans flip coins, some will get 20 heads in a row — but if they all come from Omaha, that's not luck.
• 1988 (Letter): Buffett formally critiques the "priesthood" of EMT academics. He notes that the teaching of EMT has been a "great service" to value investors — reducing competition by telling prospective analysts that analysis is useless.
• 1998 (Meeting): The most direct and public formulation. Buffett compares business schools teaching EMT to medical schools teaching that germs don't cause disease. The doctrine is not merely wrong; it is actively harmful because it suppresses the formation of the critical thinking skills that could otherwise identify mispricings.
  • The Paradox: The widespread adoption of EMT has been a "great gift" to those who don't believe it. "It has been helpful to us that so many schools have taught their students that it didn't make sense to think."
  • The Evidence: The Buffett 43-year record, the Graham disciples' records, and the empirical reality of market panics (1987, 1998 LTCM, 2000 dot-com, 2008 GFC) all demonstrate that prices can diverge sharply from value for extended periods.
• Ongoing: Every subsequent market panic provides a new natural experiment. In each case, the EMT prediction (prices are always correct) fails visibly. Berkshire's consistent ability to deploy capital opportunistically during panics — BNSF in 2009, Goldman Sachs preferred in 2008, the equity portfolio rebuilds in 2020 — is the ongoing empirical refutation.

💬 Primary Source Quotes

"It has been helpful to us that so many schools have taught their students that it didn't make sense to think." — Buffett, 1998 Meeting

"Our Graham-and-Doddsville crowd... have simply exploited gaps between price and value. They all know they are buying a dollar for fifty cents, and that's the whole thing." — Buffett, 1984 Columbia lecture

"I find it extraordinary that the same professors who teach the random-walk theory send their students off to spend 40 hours a week practicing fundamental analysis." — Buffett, paraphrased, multiple meetings

🔗 Connections

• Related Concepts: Intrinsic Value, Risk Arbitrage, Margin of Safety, Value Investing, Circle of Competence, The Superinvestors of Graham-and-Doddsville, Mr. Market
• Related Entities: Warren Buffett, Charlie Munger, David L. Dodd, Walter Schloss
• Key Sources: 1988 Letter, 1998 Meeting, 1999 Meeting, 2006 Letter
• Index: index