During my day with Eric Hanushek, he repeatedly asked me, "If rising worker productivity doesn't come from education, where does it come from?" Good question. In the pre-modern world, workers got little education and had low productivity. In the modern world, workers get much education and have high productivity. Productivity (and education!) keep going up.  If formal academic training isn't the main reason, what is?

The safe answer is, "I don't know. But whatever the answer is, it's not education." However, safe answers are not my style. While I'm not sure, I think I've got a pretty good guess. Or to be more precise, two pretty good guesses. To what does the modern worker owe his high productivity?