Sunspotter: I disagree that Buffett's method is totally obvious or well known. I learned two things from that Yale paper and I've been investing a very long time, starting at age 19. I've read all the texts associated with Early Buffett. Over the decades I've perused umpteen write-ups about Buffett, and much of what he's written himself.
1) Most commentators have always assumed that Buffett's superior performance was due in part to his successful non-public holdings and his skill in running them. But the article says BRK's private firm performance lagged that of the public holdings. So foremost, Buffett is a great stock picker rather than a great manager.
2) While many investors know that BRK stocks are low PE and rather conservative, they probably assume that BRK has been capitalized in a likewise conservative way. However Buffett's portfolio has been leveraged at an aggressive 1.6:1 . That consistently high leverage since 1976 elevated BRK's performance from very good to the best in the world.
Thanks for posting that.