Ten more billionaires have signed on to the Giving Pledge, which enters its fifth year.
The effort, started by Warren Buffett and Bill and Melinda Gates, encourages billionaires to give the majority of their wealth to philanthropic causes.
Those joining the list this year cited a number of causes—from helping refugees to advancing medical research—that they will support, as well as many sources of inspiration for their decision.
"My philanthropic DNA was inherited from my mother, who dedicated her life to the service of others," said John "Jay" Jordan, the co-founder of private equity firm the Jordan Co. "[She] told me that in her view the true measure of financial philanthropy is not how much one gives but how much one has left after one gives. That sets the bar pretty high and would suggest that perhaps a 50 percent hurdle is too low."
Of course, some of those who pledge give much more than 50 percent, including Judy Faulkner, who joined the list this year. The CEO and founder of electronic health records company Epic said she plans to give away 99 percent of her net worth, which is currently estimated to be about $2.6 billion, according to Forbes.
From its initial list of 40 families, the Giving Pledge now includes 137 pledgers from 14 countries.
"We hope to intensify philanthropy and encourage people to get started younger," said Bill Gates.
There are two billionaires on this year's list of pledgers who are under 50 years old, Chobani founder Hamdi Ulukaya and Groupon co-founder Brad Keywell.
The 10 new signatories are:
Harold Grinspoon and Diane Troderman
Gordon and Llura Gund
Elie and Susy Horn
John W. "Jay" Jordan II
Brad and Kim Keywell
Ruth and Bill Scott
Sunny and Sherly Varkey
Sir Ian Wood