What studies are these? Because I definitely am not going to buy that without a serious study. 10-15 seems way too low. Personally, I really see no reason to risk going after Alpha when you can slowly accumulate plenty of money over the long term so long as you just follow the market.
You might like his investment theories then since he heavily favors investing in high risk sectors such as small cap value and diversifying risk to hit small value, large, and beta while allocating a greater percentage of the portfolio to bonds. Basically, so you wont take a big hit in a bear while getting good returns in a bull.
Like I said, i dont have that data. And since the article is referencing a study conducted by a group for his firm, you'll likely have to pay to see it or ask him in that thread I posted and he'll should be better able to defend this than I can
Perhaps not the study you're looking for, but since I don't have a computer handy, this should explain the mathematical concept pretty well: http://www.investopedia.com/articles/01/051601.asp. I will admit that memory failed me here, the actual number appears closer to 20, although the point stands nonetheless
Also, as a matter of fact, I generally don't like small caps because most of them are either lower quality companies based on fundamentals, or utterly overvalued. I'm not saying there aren't good small companies, but the good ones are drowned in a sea of unprofitable, crappy companies due to the sheer amount of them.