Here's an interesting read...Imitation is indeed the sincerest form of flattery.
The link to the entire paper is below the abstract.
We analyze the performance of Berkshire Hathaway's equity portfolio and explore potential explanations for its superior performance. Contrary to popular belief we show Berkshire's investment style is best characterized as a large-cap growth. We examine whether Berkshire's investment performance is due to luck and find that beating the market in 28 out of 31 years places it in the 99.99 percentile; however, incorporating the magnitude by which Berkshire beats the market makes the “luck” explanation unlikely even after taking into account ex-post selection bias. After adjusting for risk we find that Berkshire's performance cannot be explained by assuming high risk. From 1976 to 2006 Berkshire's stock portfolio beats the S&P 500 Index by 14.65%, the value-weighted index of all stocks by 10.91%, and the Fama and French characteristic portfolio by 8.56% per year. The market also appears to under-react to the news of a Berkshire stock investment since a hypothetical portfolio that mimics Berkshire's investments created the month after they are publicly disclosed earns positive abnormal returns of 14.26% per year. Overall, the Berkshire Hathaway triumvirates of Warren Buffett, Charles Munger, and Lou Simpson posses' investment skill consistent with a number of recent papers that argue investment skill is more prevalent than earlier papers suggest.