Knowing how to keep someone motivated and how to keep a connection are skills humans have learned and evolved over hundreds of thousands of years. A robot can't figure out whether you can do one more push-up, or how to motivate you to actually do it.

It's most useful to think about not jobs but tasks. And within any given job, there are lots of different tasks. If you're a radiologist maybe reading the images machines can be able to do that better, maybe making the broader diagnosis and communicating it to the patients.

Machines already are much smarter than us at so many things. I mean, try to multiply two 10-digit numbers with each other or, you know, sift through a thousand documents. So there's lots of things that machines are better at including in mental task than us. There's many more that they're not as good at, but the direction is pretty obvious and the progress is clear.

But the broader lesson of the first Industrial Revolution is more like the Indy 500 than John Henry: economic progress comes from constant innovation in which people race with machines. Human and machine collaborate together in a race to produce more, to capture markets, and to beat other teams of humans and machines.

For a long time, the humans are going to be better than the machines and so different parts of the job will be leveraged. In a way that's happened for centuries, and we've adapted. And it's made the people who had parts of their jobs automated more valuable and more productive to the extent that they are essential for the other components of their jobs.

The economy in the next 20 to 25 years is going to change more than they did in the last 20, 25 years. And that's because exponential trends are affecting a bigger and bigger share of the economy. So we have some huge disruptions in store, and I can't predict exactly what the innovations are going to be. If I did, I would have already invented them. But I think they'll be comparable to the innovations we saw in the past 20, 25 years if not greater.

Electricity is an example of a general purpose technology, like the steam engine before it. General purpose technologies drive most economic growth, because they unleash cascades of complementary innovations, like lightbulbs and, yes, factory redesign.