As of 4-6-07: Warren Buffett's Berkshire Hathaway (BRK.B) has disclosed a greater than 10% stake in Burlington Northern Santa Fe (BNI). Through three insurance subsidiaries (Columbia, National Indemnity, and National Fire & Marine) Berkshire beneficially owns 39,027,430 shares of Burlington Northern common stock according to an SEC filing made on Friday, April 6, 2007. This is the biggest single common stock investment made by Berkshire in a long time and turns out to be one of the two mystery investments Buffett referred to but wouldn't disclose in his annual letter.

12/9/06 In an amended 13D filing after the close Friday on USG (NYSE: USG), Warren Buffett's Berkshire Hathaway disclosed a 19% stake (17.07 million shares) in the company. From August 23, 2006 through October 4, 2006, subsidiary NICO acquired 1,112,900 shares of USG Common Stock through open market purchases. Buffett's group bought 734.7K shares on 08/23 at $45.90, 7K shares on 08/24 at $46.03 and 371.2K shares on 10/04 at $46.10. % of portfolio: 1.7% Increased position by +2.22%

% of portfolio: 18.2%

% of portfolio: 17.4%

% of portfolio: 13.7% Increased position by +7.02%

% of portfolio: 12.1%

% of portfolio: 6.2%

% of portfolio: 4.9%