Shares of Berkshire Hathaway Inc. Cl B slipped 0.71% to $468.86 Tuesday, on what proved to be an all-around mixed trading session for the stock market, with the S&P 500 Index rising 0.40% to 5,916.98 and the Dow Jones Industrial Average falling 0.

That might explain why the Bill & Melinda Gates Foundation has Berkshire as its second biggest holding, behind only Microsoft. As of the latest reporting period, the foundation owns 24.6 million shares of Berkshire worth around $10 billion, making up 21% of its total portfolio.