After reading the statement above again. Two things jumped out. There were food shortages into the 1950’s. Even upper middle class families typically only had one car into the 60’s. So every household member of driving age didn’t typically have their own car like you see know.
Discussion
In other words , people had more of an incentive to exercise?
I think a useful metric to consider, and this was inspired by what you were saying, are the difference in reasons for somebody to leave their place of residence.