In 1920: agriculture was 27% of labor force: http://www.agclassroom.org/gan/timeline/farmers_land.htm

Now, 2-3%. One in 4 people had their profession superseded. A lot of that slack was taken up by industry (and war and death), but that took 20-30 years to catch up.

Is there a pool of work for people to absorb 25% of the present labor force? Most of the emerging technologies I see are labor-saving, not labor consuming.

Two possibilities for big labor demand in the next few decades: - healthcare and assistance for the elderly - removing development restrictions in booming cities, unleashing an epic (or Chinese-level) building boom

Both have fundamental political foundations and won't be solved solely by technology.