i think is high alpha is primarily due to his stock picking abilities. he picks stocks which are relatively undervalued in the market and thus makes a small fortune when others come to know of it. Its the Buffets reputation more than anything else that has been giving him returns. off course he has a record to prove that he deserves that reputation. I am not going to comment if he or others manipulate the market but when small timers come to know of his intentions or investments they make a beeline for whatever he is buying into. This coupled with leverage and low interest rates Berkshire enjoy all team up and give him a grand return on his investments. Small timers with their inherent habit of over reacting and non reaction are not able to mimic the moves of warren buffet and as rightly said he is not required by law to tell us what he owns or has his money into.