I think comparing 1870-1970 period and 1970-onwards is a bit unfair. We kind of know exactly why productivity exploded on n that period, and it is all to do wi

I think comparing 1870-1970 period and 1970-onwards is a bit unfair. We kind of know exactly why productivity exploded on n that period, and it is all to do with (later stages of) Industrial Revolution. All these people living on $1 / day suddenly started using machines providing power and automation. The cold water heated on fire was replaced by plumbing not by magic, but by availability of cheap pipes and boilers. So basically, some time in 18th century, we figured out one trick, then milked it like crazy, and around 1970s we reaped most of the benefits of that one trick. But now we're back to the pre-industrial revolution situation, where we are looking for various marginal improvements. Yes, there are other effects like rising inequality (so marginal improvements going to the owners not workers) but I don't see why you would extrapolate productivity growth from 1870-1970 and assume you can keep on achieving that. Who knows, maybe AI will do that, multiplying human intelligence the way the steam engine multiplied human strength.