Buffett has teamed up with Bill Gates to convince 40 billionaires (so far) to give half their fortunes away to charity. A look at the numbers behind the "Giving Pledge"

Warren Buffett and Bill Gates, America's two wealthiest individuals, have convinced a growing number of U.S. billionaires to donate a minimum of 50 percent of their vast fortunes to charity. (Watch a report about the charitable acts.) The so-called "Giving Pledge" has been described as a "moral commitment," and carries no legal weight. Around 10 percent of America's billionaires have signed the pledge so far, but Buffett hopes to recruit more. "Every saint has a past, every sinner has a future," he told reporters. "We’ll keep on working." Just how much will the Giving Pledge benefit the world's poor and needy? Here, a look at the numbers:

40
Number of U.S. billionaires who've signed the pledge, so far. The list includes CNN mogul Ted Turner, hotel heir Barron Hilton and Star Wars director George Lucas

$158.8 billion
Total amount pledged so far

70 to 80
Number of people Buffett and Gates have contacted about joining their charitable campaign

0
Number of billionaires that Buffett claims mentioned taxes when consulted about signing the pledge

6
Number of people on Forbes' list of the ten wealthiest individuals in the U.S. who have not signed the pledge

99
Percentage of Warren Buffett's $47 billion fortune that he plans to donate to charity

403
Total number of billionaires currently living in the United States

$1.2 trillion
Combined net worth of all America's billionaires, which make up about 40 percent of billionaires worldwide

$600 billion
Approximate amount the pledge would generate for charity, if all of America's billionaires signed on

$303 billion
Amount donated to charity by American foundations, corporations and individuals in 2009

$5 billion
Amount pledged to the reconstruction of Haiti by the world's governments, foundations and individuals. The amount so far raised by the Giving Pledge would pay for the estimated $14 billion reconstruction of Haiti 11 times over.

$2
Daily income of two-thirds of the world's population, according to the U.S. Agency for International Development