When I was trying to figure out why lives have improved so much in the last 300 years, where we've gone from a third of kids dying before 5 to - by 1990 it was down to 10% - now it's down to 5%. And saying why, over all history, there were smart people, but that number didn't change. Average life span didn't change. What's magical about what's been deemed the Industrial Revolution? It's really energy intensity.

India just went 3 years with no cases [of polio]. Pakistan is our toughest location right now because some parts of the Taliban have not allowed vaccinators to come in and have even attacked vaccinators. We are hopeful this will get resolved since no one wants their kid to be paralyzed. I spend a lot of time making sure the polio campaign is doing the best it can. We have great computer models that help guide our activities.

I hope corporations will dedicate a percentage of their top innovators' time to issues that could help people left out of the global economy. This kind of contribution is even more powerful than giving cash or offering employees' time off to volunteer. It is a focused use of what your company does best. It is a great form of creative capitalism, because it takes the brainpower and makes life better for the richest, and dedicates some of it to improving the lives of everyone else.

The nuclear industry has this amazing record, even equipment from generations one and two. But nuclear mishaps tend to come in these big events - Chernobyl, Three Mile Island, and now Fukushima - so it's more visible.

My wife thinks she's better than me at puzzles. I haven't given in on that one yet.

When I was growing up, my parents were almost involved in various volunteer things. My dad was head of Planned Parenthood. And it was very controversial to be involved with that.

I believe the government has the right to recover from the heirs to the fortunes of its most successful citizens some portion of those fortunes.