The $2.8 billion is the most that Buffett has donated to charities since he began making annual gifts in 2006, showing that Buffett is committed to giving away an unprecedented sum of money in his lifetime, says Rebecca Riccio, director of the Social Impact Lab at Northeastern University.

She says Buffett considers these to be smart philanthropic investments because he trusts the Gates Foundation to use his money effectively in a way that is aligned with his personal values and interests.

“He wants it to be used wisely, but acknowledges that he doesn’t have the time or expertise required to engage in effective grant making,” Riccio said. “Instead, he takes what he calls a ‘wholesale approach’ by leveraging his talent for identifying good investment opportunities, and making a small number of extremely large gifts to the Gates Foundation.”