From The Baseline Scenario:
Random Variation
By James Kwak
As I previously wrote on this blog, one of my professors at Yale, Ian Ayres, asked his class on empirical law and economics if we could think of any issue on which we had changed our mind because of an empirical study. For most people, it’s hard. We like to think that we form our views based on evidence, but in fact we view the evidence selectively to confirm our preexisting views.
I used to believe that no one could beat the market: in other words, that anyone who did beat the market was solely the beneficiary of random variation (a winner in Burton Malkiel’s coin-tossing tournament). I no longer believe this. I’ve seen too many studies that indicate that the distribution of risk-adjusted returns cannot be explained by dumb luck alone; most of the unexplained outcomes are at the negative end of the distribution, but there are also too many at the positive end. Besides, it makes sense: the idea that markets perfectly incorporate all available information sounds too much like magic to be true.
But that doesn’t mean that everyone who beats the market is actually good at what he does, even if that person gets a $100 million annual bonus. That person would be Andy Hall, the commodities trader who stirred up controversy when he apparently earned a $100 million bonus at Citigroup—in 2008, of all years. (That was a year with huge volatility in the commodities markets.)...MORE
