To no one’s surprise, topping it was Facebook founder Marc Zuckerberg and his wife, who gave a billion dollars to the Silicon Valley Community Foundation. The list also included other well-known figures, such as Michael Bloomberg, George Soros and Nike’s Phil Knight.

But many of the biggest givers were people who are not household names, except perhaps, in their own communities. People such as William Ridgeway, an eye doctor, investor, and Indiana University graduate, who made the list by leaving $39 million in his will to the University of Evansville, in his hometown.

Most of the other donors also founded their own businesses. Only three inherited substantial wealth.

This underscores what broader surveys have shown: People who earned their fortunes are more likely to be generous than those who did not. And that’s not just the case for the very rich. Although the 50 most generous donors gave nearly $8 billion to charity last year, ordinary Americans gave 30 times as much from their paychecks.

What distinguishes philanthropy in the United States from giving in other countries is that a very large share of the American population does it.

Some argue that wealthy donors have the ability to contribute even more than they do, and that their gifts too often go to organizations—well-financed museums, hospitals and universities—that don’t need their money as much as charities that work with needy people. But it’s their money, and making donations to organizations that are personally meaningful has a lot to do with why they give at all, just as it does for the rest of us.