Like my friend Warren Buffett, I feel particularly lucky to do something every day that I love to do. He calls it "tap dancing to work."

A top-quartile teacher will increase the performance of their class - based on test scores - by over 10 percent in a single year. ... That means that if the entire U.S., for two years, had top-quartile teachers, the entire difference between us and Asia would go away.

My dream is that every child has enough food to eat, good medical care, and the chance to go to school and even attend college.

So on the demand side [for energy], there have been a variety of policies that globally have been way over $50 billion a year of tax credits, raising the price of electricity through things like renewable portfolio standards, so the total amount of money that's gone into sending a price signal to push up demand versus what would happen without it has been gigantic.

In low-income countries, getting to a health post is hard. It's very expensive.

Ninety percent of the cases of polio are in security-vulnerable areas.

People want to watch whatever video they want to watch whenever they want to watch. If you provision your Internet infrastructure adequately, you can do that.