Probably the number one concern among Berkshire Hathaway (BRKA) followers is the successorship of Warren Buffett. Buffett is in his mid seventies and clearly will not be around forever. What will happen when the cockpit is turned over to someone else? Will someone else be as investment savvy as Buffett? Surely not. Will Berkshire stock drop as Buffett himself is most likely valued highly by current shareholders?

Many people think Lou Simpson will take over for Buffett when the time comes. Simpson is the CEO of capital operations for Geico. Basically, he manages the float for Geico's insurance business, which amounts to several billion dollars. Interestingly, while Buffett gets the credit for portfolio additions to Berkshire's investment portfolio, often the smaller buys are the work of Simpson, not Buffett.

Taking a look at Berkshire's holdings as of June 30th, we can get a good idea of which investments are the work of Buffett, and which have Simpson's fingerprints on them. Buffett's largest holdings are the ones he has held for years. Gillette, Coca-Cola, Wells Fargo, American Express, Washington Post, to name a few. After subtracting Berkshire's top 10 holdings (mostly those older buys) as well as its position in Proctor and Gamble (due to the pending merger) and PetroChina (which was one of BRK's largest holdings until it was trimmed dramatically in the first half of 2005), Berkshire's $35 billion public company portfolio is narrowed down to less than $3 billion invested in 20 companies.

Since Buffett has stated in the past that Simpson manages about $2.5 billion, it is safe to assume this small portion represents what investors should expect to see on their position sheets should Simpson be named Buffett's successor. As a result, more often than not relatively small new additions to BRK's portfolio are the work of Simpson, not Buffett himself.