The top five U.S. donors in 2013 accounted for nearly half of all giving by the top 50 U.S. philanthropists, according to a CNN Money analysis.
The top donors, in order of generosity, were:
1. Mark Zuckerberg and Priscilla Chan, Facebook CEO: $992 Silicon Valley Community Foundation
2. George Mitchell Fracking pioneer (deceased) $750 Cynthia and George Mitchell Foundation
3. Philip and Penelope Knight Nike co-founder $500 Oregon Health & Science University Foundation
4. Michael Bloomberg Former NYC mayor, founder of Bloomberg L.P. $452 Arts, education, environment, public health and other causes
5. John and Laura Arnold Hedge fund founder $296 Laura and John Arnold Foundation, Fidelity Charitable Gift Fund