Introduction: The Secret Behind the Oracle’s Alpha
While much has been said and written about Warren Buffett and his investment style, there has been little rigorous empirical analysis that explains his performance. Every investor has a view on how Buffett has done it, but we seek the answer via a thorough empirical analysis in light of some the latest research on the drivers of returns.
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.
So how large is this Sharpe ratio that has made Buffett one of the richest people in the world? We find that the Sharpe ratio of Berkshire Hathaway is 0.76 over the period 1976-2011. While nearly double the Sharpe ratio of the overall stock market, this is lower than many investors imagine. Adjusting for the market exposure, Buffett’s information ratio2 is even lower, 0.66. This Sharpe ratio reflects high average returns, but also significant risk and periods of losses and significant drawdowns.
If his Sharpe ratio is very good but not super-human, then how did Buffett become among the richest in the world? The answer is that Buffett has boosted his returns by using leverage, and that he has stuck to a good strategy for a very long time period, surviving rough periods where others might have been forced into a fire sale or a career shift. We estimate that Buffett applies a leverage of about 1.6-to-1, boosting both his risk and excess return in that proportion. Thus, his many accomplishments include having the conviction, wherewithal, and skill to operate with leverage and significant risk over a number of decades.
This leaves the key question: How does Buffett pick stocks to achieve this attractive return stream that can be leveraged? We identify several general features of his portfolio: He buys stocks that are “safe” (with low beta and low volatility), “cheap” (i.e., value stocks with low price-to-book ratios), and high-quality (meaning stocks that profitable, stable, growing, and with high payout ratios). This statistical finding is certainly consistent with Buffett’s writings, e.g.:
Whether we’re talking about socks or stocks, I like buying quality merchandise when it is marked down
– Warren Buffett, Berkshire Hathaway Inc., Annual Report, 2008.
Interestingly, stocks with these characteristics – low risk, cheap, and high quality – tend to perform well in general, not just the ones that Buffett buys. Hence, perhaps these characteristics can explain Buffett’s investment? Or, is his performance driven by an idiosyncratic Buffett skill that cannot be quantified?
The standard academic factors that capture the market, size, value, and momentum premia cannot explain Buffett’s performance so it has to date been a mystery (Martin and Puthenpurackal (2008)). Given Buffett’s tendency to buy stocks with low return risk and low fundamental risk, we further adjust his performance for the Betting-Against-Beta (BAB) factor of Frazzini and Pedersen (2013) and the Quality Minus Junk (QMJ) factor of Asness, Frazzini, and Pedersen (2013). We find that accounting for these factors explains a large part of Buffett’s performance. In other words, accounting for the general tendency of high-quality, safe, and cheap stocks to outperform can explain much of Buffett’s performance and controlling for these factors makes Buffett’s alpha statistically
To illustrate this point in a different way, we create a portfolio that tracks Buffett’s market exposure and active stock-selection themes, leveraged to the same active risk as Berkshire. We find that this systematic Buffett-style portfolio performs comparably to Berkshire Hathaway.