Truly, it was the greatest century

DeLong on the Greatest Completed Century So Far: 

Briefly: very very roughly, approximately, and inadequately, on average what twenty workers were needed to do in 1870 with their eyes, fingers, thighs, brains, mouths, and ears, 1 worker was able to do in 2010.

It is also true that what one worker could do in 1870 required 20 in -6000. But that 20-fold amplification was an 8000-year creep rather than a 140-year sprint: a proportional growth rate of 0.04%/year rather than 2.1%/year. And from -6000 to 1870 the overwhelming bulk of the potential benefits for humans from that twentyfold upward creep of technological knowledge had been eaten up by growing resource scarcity: the land and other natural resources available to support 1 person in -6000 had to support 400 by 1870.

By contrast, the twentyfold post-1870 technological-progress wave had to deal not with a 200- but only a 6-fold multiplication of human numbers, leaving lots to be devoted to bringing about much higher average productivity.

Productivity increases really really matter. 

If there is one single nugget of insight that I want readers of my book Slouching Towards Utopia to permanently engrave on their brains, this is it: around 1870 the rate of technological progress and thus of potential wealth creation went into much higher gear. After 1870, humanity's deployed technological capabilities and thus potential prosperity doubled every thirty-five years—and with it came economic creative destruction that reduced old economic structures to rubble and built new ones, and did it again, and again, and again, every single generation. Before 1870? From 1770-1870 humanity's globally-deployed technological prowess had a doubling time of about 150 years—not 35. From 1500-1770 it had a doubling time of 500 years. And before 1500, we are looking at a doubling time of 2000 years. The difference between our world, in which technological progress creatively destroys and revolutionizes the economy every 35 years, and the world of Agrarian-Age antiquity in which the same proportional changes in technology and economy, and thus in polity and society, take not 35 but 2000 years is, I think, a master force shaping human history.

I want to hammer home the obvious to those who don't have exponential growth magnitudes in their immediate intellectual panoply: a twentyfold amplification of human technological prowess in 140 years is a REALLY BIG F---ING DEAL. To get an equivalent proportional jump in the other direction, you have to go back from 1870 to the Bronze Age— to the year -2000 or so. We are, proportionately, as separate in technology from the railroad's Golden Spike and the first transoceanic cables as those were from the earliest chariots and the sculptor of the dancing girl of Mohenjo-Daro: