If you want to see the thinking of one who has, simply follow the advice quoted here (though I will note that the post was laced with irony). Jeffrey Sachs noted that the 3.5 trillion USD net worth of the world's 950 billionaires spins of $175 billion annually at the 5% payout rate practiced by most US foundations.
“... $175bn per year – that would do it. Then we don’t need the G8 but 950 people on the Forbes list,” said Mr Sachs. “Maybe private philanthropists will champion solutions to individual problems rather than the G8,” he said.The Panelist, who brought the quote to my attention, noted that $175 bn would also fund the US/Iraq war and perhaps the billionaires would like to pick up that tab.