Dr. Rajiv J. Shah doesn't just talk about solving some of the world's biggest problems, he does something about it.
With the Bill & Melinda Gates foundation, he helped forge a plan to vaccinate 900 million children.
At the US Agency for International Development, he led the American response to an earthquake in Haiti and an Ebola outbreak in West Africa.
Now he's president of the Rockefeller Foundation and argues that making incremental improvements doesn't get the results, no matter what the scale of the problem. He offers his philosophy in his new book, Big Bets: How Large-Scale Change Really Happens.