How much do billionaires give?
In June, Warren Buffett and Bill and Melinda Gates challenged the nation's billionaires to give away at least half of their net worth. Here's how 9 big spenders dole out their money.
New York City Mayor Michael Bloomberg has pledged $375 million to reduce tobacco-related deaths.
He has also agreed to be a part of Warren Buffett's group of billionaires who agree to give away at least half of their net worth.
NEXT: Pierre and Pam Omidyar
Last updated December 14 2010: 8:44 PM ET