Eugene Fama

After costs, only the top 3% of managers produce a return that indicates they have sufficient skill to just cover their costs, which means that going forward, and despite extraordinary past returns, even the top performers are expected to be only as good as a low-cost passive index fund. The other 97% can be expected to do worse.

People are always saying that prices are too high. When they turn out to be right, we anoint them. When they turn out to be wrong, we ignore them. They are typically right and wrong about half the time.

The market is incredibly inefficient and capable on rare occasions of being utterly dysfunctional. And people have a really hard time getting their brain around that fact. They want to believe that it's approximately efficient almost all the time, and it simply isn't true.