The efficient market hypothesis, as it is generally understood, stands in stark opposition to investors who believe they can beat the market and identify opportunities that the broader market ...

But maybe not so much any more. In a new paper called The Less-Efficient Market Hypothesis, Mr. Asness argues that markets have grown increasingly erratic in recent decades.

The Efficient Market Hypothesis argues that no investment strategy or signal can consistently outperform a simple buy-and-hold approach to broad stock averages over time. However, there is plenty ...