Pledging money to charity is one thing; actually writing a check to your preferred cause is quite another. In partnership with Shook Research, headquartered in Boca Raton, Fla., FORBES uncovered who put hard cash behind their philanthropic promises in 2015. We looked beyond gift commitments and money sitting in foundations to reveal how much actually reached beneficiaries. (See the full methodology here.)

“We’re seeing more givers who were formerly donating anonymously now willing to give openly as a way to inspire others to follow their lead,” says RJ Shook, founder of Shook Research. “These are the real role models in the world of philanthropy.”

Four of the five biggest philanthropic givers in 2015 were also among the 20 richest Americans on The Forbes 400. Leading the pack by far was esteemed investor Warren Buffett, who gave away $2.84 billion in 2015, mostly by gifting Berkshire Hathaway stock to his buddy Bill Gates’ foundation. The Microsoft cofounder, who is the richest person on the planet, wasn’t too far behind, distributing $1.4 billion through the Bill & Melinda Gates Foundation, the world’s largest private philanthropic foundation (that figure excludes the share of funds distributed that came from Buffett’s gifts).

Hedge fund titan George Soros, who donated $654 million, and former New York City mayor Michael Bloomberg, who shelled out $510 million, were also in the top five.

Joining these well-known billionaire philanthropists were Stefan Edlis and Gael Neeson, Chicago art collectors who donated 44 works worth an estimated $400 million to the city’s Art Institute, including pieces by Andy Warhol, Roy Lichtenstein and Jasper Johns. Edlis, who is 91 years old, sold his Apollo Plastics for $15 million in 2000. The couple’s foundation gave another $113 million to the Aspen Art Museum and Lyric Opera of Chicago, among others recipients, making them this year’s fourth-biggest givers.

Other newcomers to the list are Liz Simons and Mark Heising, whose foundation donated $43 million to early childhood education, climate change research and other causes. She is the daughter of retired hedge fund billionaire James Simons, who along with his wife, Marilyn, are also on the Top Givers list. They contributed $298 million in 2015, primarily to education and research on math and basic sciences. Read more about how the Simons family cultivated philanthropy across generations here.

Of the philanthropists who were on the 2014 Top Givers list, Barry Diller and Diane von Furstenberg stepped up their gifts most steeply. The digital media executive and fashion designer doled out more than $100 million – two-thirds of their promised amount – in 2015 toward a controversial plan to build Pier55, a public park and performance space on the Hudson River in Manhattan. In 2014, they gave away $26.5 million.