The year I was born, 1955, the first big disease-eradication program in the world was declared for malaria. After about a decade of work, they realized that, at least in the tropical areas, they did not have the tools to get it done.

By almost any measure, the world is better than it has ever been. People are living longer, healthier lives. Many nations that were aid recipients are now self-sufficient. You might think that such striking progress would be widely celebrated, but in fact, Melinda and I are struck by how many people think the world is getting worse. The belief that the world can’t solve extreme poverty and disease isn’t just mistaken. It is harmful. That’s why in this year’s letter we take apart some of the myths that slow down the work. The next time you hear these myths, we hope you will do the same.

(Talking about his first computer) Like all kids we not only fooled around with our toys, we changed them. If you've ever watched a child with a cardboard carton and a box of crayons create a spaceship with cool control panels, or listened to their improvised rules, such as "Red cars can jump all others," then you know that this impulse to make a toy do more is at the heart of innovative childhood play. It is also the essence of creativity.

In the same way that when the car got going, people thought it would be an electric car, people thought it would be a steam car.

I don't like typing messages on my phone. Some people get used to it.

Natural epidemics can be extremely large. Intentionally caused epidemics, bioterrorism, would be the largest of all.

We need to look at less obvious paths, things like the wind in the jet stream, which is very high up. The material science of what type of kite string you would need to connect up to that. That's still at the basic research level.