Last July's contribution of 19.3 million shares was worth $1.5 billion at that day's closing price of $82.54.

In a 2006 letter to Microsoft's chairman and his wife, Buffett outlined a long-term schedule that has him donating 5 percent fewer shares each July year-over-year.



Over the eight years, Buffett has given the Gates Foundation more than 168 million shares, about a third of the 500 million shares he has pledged.

The total value of those gifts on the days they were made is almost $13 billion. At today's closing price, the shares would be worth $19.4 billion.