耶鲁教授：市场效率理论崩溃的瞬间

John Geanakoplos, Yale professor and hedge fund co-founder:

"the Dow fell from 14,000 to 6,500. did American companies really become worth 50% less?" this is where standard financial theory starts breaking.

markets are supposed to absorb all available information into the price. the idea became so influential that economists argued a monkey throwing darts could compete with professional investors.

but then the professors who helped build that theory went to Wall Street and made fortunes trading the same markets they said were almost impossible to beat.

Geanakoplos thought finance was missing something much bigger. collateral. leverage. and what happens when both disappear at the same time.

because a market can be incredibly efficient at processing information while still producing a completely distorted price when the financial system underneath it changes. and he demonstrates the first part in less than two minutes. - 16 Yale students. - different private information. - no trading experience.

they start trading with each other and produce 5 trades around $20–25 - almost exactly where the theoretical market-clearing price should be. no single person knew the answer. the market found it. this is why the lecture is worth watching.

not because it teaches you how to predict the next candle, but because it forces you to separate two things most traders treat as the same: the information inside a price + and the mechanism that created that price.

finance was once considered too practical for Yale to even take seriously as an academic field. then Wall Street started hiring physicists and mathematicians by the thousands.

the lecture is free and the most important question in it is probably the one traders almost never ask: before trying to predict where price goes next, do you actually understand why the current price exists?