Jim Simons has stepped down as the chairman of Renaissance Technologies LLC, commonly regarded as the most successful quant hedge fund in history. This marks the end of an era in finance. Throughout Simons’s storied career, Renaissance proved that the finance textbooks — which claim that the market can’t be beaten consistently — were wrong. But the limitations of Renaissance’s success show that the textbooks aren’t completely crazy, either.
The core of basic finance theory is the Efficient Markets Hypothesis. This says that the only way to get consistently higher returns in the stock market is to accept higher risk. The reasoning is that since financial markets involve so many skilled participants all trying to figure out the right price for assets, no trader will be able to retain an informational advantage for very long — if you hit on a winning strategy, it won’t be long before someone else figures it out and copies it, and your advantage is competed away.