Warren Buffett may trust Bill Gates to spend his money wisely, but Gates has been wise to defer to his long-standing friend on how best to invest it.

Several months after the “sage of Omaha” promised most of his fortune to the Bill and Melinda Gates Foundation in 2006, his pledged Berkshire Hathaway shares were its largest single equity stake. And they out-performed the foundation’s other investments, offering an early hint of Buffett’s overtaking of Gates this year as the world’s richest man, according to Forbes magazine’s annual rankings.