In its annual report for 2011, Berkshire Hathaway (BRK.A) (BRK.B) reported common stock investments in eleven companies that each had a market value exceeding $1 billion.  However, there has been only one of these companies that Warren Buffett has been adding to every year since 2005.

That company is Wells Fargo (WFC).   Berkshire further added to its stake in Wells Fargo during the first quarter of 2012.

Currently, Wells Fargo is Berkshire’s second largest investment, valued at $13.7 billion.  (Berkshire’s largest common stock investment is in Coca-Cola (KO), with a market value of $15.6 billion.  Berkshire’s third largest investment is in IBM (IBM), which has a market value of $12.6 billion.)

In 1990, Berkshire Hathaway made an initial investment in Wells Fargo of $289 million (5 million shares). That position was relatively stable from 1990 through 2004.  (In 1998, Wells Fargo merged with Norwest and each share of Wells Fargo was converted into 10 shares of the “new” Wells Fargo.) 

Source: Why Warren Buffett Keeps Adding To His Wells Fargo Investment – Business Insider