Excerpt:

Berkshire Hathaway has realized a Sharpe ratio of 0.76, higher than any other stock or mutual fund with a history of more than 30 years, and Berkshire has a significant alpha to traditional risk factors. However, we find that the alpha becomes insignificant when controlling for exposures to Betting-Against-Beta and Quality-Minus-Junk factors. Further, we estimate that Buffett’s leverage is about 1.6-to-1 on average. Buffett’s returns appear to be neither luck nor magic, but, rather, reward for the use of leverage combined with a focus on cheap, safe, quality stocks. Decomposing Berkshires’ portfolio into ownership in publicly traded stocks versus wholly-owned private companies, we find that the former performs the best, suggesting that Buffett’s returns are more due to stock selection than to his effect on management. These results have broad implications for market efficiency and the implementability of academic factors.

Buffett’s record is remarkable in many ways, but just how spectacular has the performance of Berkshire Hathaway been compared to other stocks or mutual funds? Looking at all U.S. stocks from 1926 to 2011 that have been traded for more than 30 years, we find that Berkshire Hathaway has the highest Sharpe ratio among all. Similarly, Buffett has a higher Sharpe ratio than all U.S. mutual funds that have been around for more than 30 years.

We document how Buffett’s performance is outstanding as the best among all stocks and mutual funds that have existed for at least 30 years. Nevertheless, his Sharpe ratio of 0.76 might be lower than many investors imagine. While optimistic asset managers often claim to be able to achieve Sharpe ratios above 1 or 2, long-term investors might do well by setting a realistic performance goal and bracing themselves for the tough periods that even Buffett has experienced.

In essence, we find that the secret to Buffett’s success is his preference for cheap, safe, high-quality stocks combined with his consistent use of leverage to magnify returns while surviving the inevitable large absolute and relative drawdowns this entails. Indeed, we find that stocks with the characteristics favored by Buffett have done well in general, that Buffett applies about 1.6-to-1 leverage financed partly using insurance float with a low financing rate, and that leveraging safe stocks can largely explain Buffett’s performance.

 
Source: Andrea Frazzini, David Kabiller and Lasse H. Pedersen, “Buffett’s Alpha.”