> Last I checked, the tractor and plow are doing a lot more work than 3 farmers, yet we've got more jobs and grow more food.

Not sure when you checked.

In the US more food is grown for sure. For example just since 2007 it has grown from $342B to $417B, adjusted for inflation[1].

But employment has shrunk massively, from 14M in 1910 to around 3M now[2] - and 1910 was well after the introduction of tractors (plows not so much... they have been around since antiquity - are mentioned extensively in the old testament Bible for example).

[1] https://fred.stlouisfed.org/series/A2000X1A020NBEA

[2] https://www.nass.usda.gov/Charts_and_Maps/Farm_Labor/fl_frmw...