The world today has 6.8 billion people...that's headed up to about 9 billion. If we do a really great job on vaccines, health care, reproductive health services, we could lower that by perhaps 10 to 15 percent.

We are seeing smarter philanthropy, more philanthropy, and that's true world wide. So it's kind of a movement that has a lot of accomplishments, even though as a percentage of the economy, it's still only a few per cent.

We weren't trying to just go public and get rich. There was no near-term thing. It always was this many-decades thing where there were no shortcuts and we'd sort of put one foot in front of the other.

The death of a child is an incredible tragedy all over the world. Back in 1990, about 12 percent of children were dying before they reached the age of 5.

Software was changing so fast, so unbelievable, that that got very quick adoption.

Technology is just a tool. In terms of getting the kids working together and motivating them, the teacher is the most important.

Today, we take the risk of nuclear war quite seriously, climate change not so much and epidemics least of all. But no single country, not even the United States, is well prepared. And even if one country is doing the right things to protect itself, it has to be a global thing.