The Chronicle of Philanthropy puts out a list each year of the most generous people – topping the list for 2013 is Mark Zuckerberg and Priscilla Chan. The couple gave 18 million shares of Facebook, equating to roughly $992.2 million, to the Silicon Valley Communication Fund.

The top 50 contributors made donations that totaled $7.7 billion dollars and pledges of $2.9 billion. Some of the nation’s biggest givers didn’t appear on the list because their donations were counted as pledges in previous years – such as Bill Gates and his wife Melinda.

George Mitchell, a Galveston Texas man who made his fortune in energy and real estate, was second on the list. While Nike chairman, Philip Knight and his wife Penelope of Portland, Oregon appeared third – making a $500 million challenge grant to Oregon Health and Science University Foundation for cancer research.

Nineteen people or couples, on the list, have signed the “Giving Pledge” – started by Bill Gates and Warren Buffet in 2010. These generous folks have pledged to give at least half their wealth to charity since the movement began.