Personal computing today is a rich ecosystem encompassing massive PC-based data centers, notebook and Tablet PCs, handheld devices, and smart cell phones. It has expanded from the desktop and the data center to wherever people need it - at their desks, in a meeting, on the road or even in the air.

I have drifted away from thinking about these philanthropic things. And it was only as the wealth got large enough and Melinda and I had talked about the view that wealth wasn't something that would be good to just pass to the children.

I've been studying how quickly we can get energy out to the poor countries - a lot of which are in Africa - and how little progress we've made there. There's no more electricity today in sub-Saharan Africa per person than there was 20 years ago.

The barrier to change is not too little caring; it is too much complexity.

I am surprised that in various countries, whether it's the U.K. or the U.S., you see isolationist tendencies that would tend to work against the co-operation, whether it's climate change, immigration, innovation, helping the very poorest. Those are things where you want to think across country boundaries and see a win-win-type solution.

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.

I'm going to retain a lot of Microsoft's stock.