Yea, the first few percentage points are underrated.

Dropping from 90% of the population being ~farmers to 80% of the population being farmers doubles the amount of time people can spend doing everything else including research, manufacturing, education etc.

In many ways it was equivalent to the drop from 51% being farmers all the way down to 2%. However, it wasn’t nearly as obvious because 90% farmers looks a lot like 80% of the population being farmers and the transition was relatively slow and unevenly distributed.