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. - Bill Gates