Keeping up with the Gates: Microsoft co-founder Paul Allen—who clocked in at No. 37 on Forbes’ latest billionaires list—has pledged the majority of his $13.5 billion fortune to charity. The 57-year-old announced his plans on the 20th anniversary of the Paul G. Allen Family Foundation. Allen has given about $1 billion over the years to causes in science and the arts, including the Allen Institute for Brain Science and the Experience Music Project. His giving has mostly focused on the Pacific Northwest, where he lives. His announcement comes a week after Bill Gates and Warren Buffett began publicly encouraging other billionaires to make a “Giving Pledge” and donate at least half their fortunes.