I remember growing up in the 90's, my classmates and I all thought that one of the other kids was a liar because he said he didn't have a yard (he lived in an apartment). It didn't make sense - everyone else in the class of 30+ kids lived in a house with a yard, so he must just be making stuff up. Obviously that's anecdotal evidence, but still. It was weird for a kid not to live in a single-family home back then.

You'd have to look at the size of the middle class back then, as that's what the "American Dream" scenario is based on there, but as a kid born in 1990, I can say that when my dad was looking for apartments when he was around college age in the 60s, the rule was not to rent an apartment that cost more than 25% of your salary. By the time I was around that same age in the late 2000s/early 2010s, it was 50% of your salary. Now, it's closer to 120% of your salary for those same apartments.