All fair considerations, but I think the main point is a matter of degree between the two time periods. Surely there were also less visible efficiencies that to

All fair considerations, but I think the main point is a matter of degree between the two time periods. Surely there were also less visible efficiencies that took place during the first period too, i.e. the electric fridge vs. an ice box, but that's not the point of the comparison, I think.