Bill Gates says he will donate an estimated $108 billion, 99 percent of his tech fortune, to the Gates Foundation. He also announced the foundation will now close in 2045, earlier than previously planned. The pledge is among the largest philanthropic gifts ever. It outpaces the historic contributions of industrialists like John D. Rockefeller and Andrew Carnegie when adjusted for inflation. The Gates Foundation's announcement Thursday promises steady support over the next 20 years to its grantees and partners, particularly in global health and education in the U.S. But it also signals an eventual end to the foundation’s immense worldwide influence.