Size Bias

Another bias is what I call the size bias. If you have twenty thousand traders in the market, sure enough you'll have someone who's been up every day for the past few years and will show you a beautiful P&L. If you put enough monkeys on typewriters, one of the monkeys will write the Iliad in ancient Greek. But would you bet any money that he's going to write the Odyssey next? You know that because of the sheer size of the sample, you're likely to find a lucky monkey once in a while. But the same applies to traders.