Until recently, over 98 percent of teachers just got one word of feedback: Satisfactory. If all my bridge coach ever told me was that I was 'satisfactory,' I would have no hope of ever getting better.

On the supply side, for innovation, you'd say, go look at those R&D budgets, and they haven't moved in the last 20 years. In the case of the US - which is the majority of R&D funding across every category you can name: health, energy, whatever - it's been about $5 billion a year from the Department of Energy.

With polio, we've gone several years with no polio in all of Africa, but now with this we're having to go and mop up in that whole region, so it's a bit of a setback for polio. So in parallel we have to go back and get rid of those cases.

I would counsel people to go to college, because it's one of the best times in your life in terms of who you meet and develop a broad set of intellectual skills.

There was a magical breakthrough when the computer became cheap and we could see that everyone could afford a computer.

I get more spam than anyone I know.

There's life and death in every email.