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:

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

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

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

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

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.

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

Sources: MSNBC, GlobalIssues.org, USAID, BBC, Guardian, CIA, Financial Post, Forbes, Reuters