“Modern Japanese, if reasonably well off, have 4 or 5 room houses/apartments”
Not true. More like 2 rooms. A bathroom and a central living area that serves as kitchen, bedroom, and family room.
I would have to do some research to see what the average housing is for Japanese. Nonetheless, in rural America 150 years ago, families of a dozen or more could live in one or two rooms. (I figure they camped out all the boys, unless it was freezing!)
Japan has encouraged the housing shortage by subsidizing uneconomical agriculture. Global-view, this demonstrates to me that government policies are behind a lot of so-called population problems.
Actually, tax-chick is correct here. She is wrong only if you consider the average Japanese as someone who lives within 30 minutes or so of Central Tokyo. Then, those who aren't so well off can afford little more than an apartment with a couple of 5 mat (a tatami mat is roughly 2 square meters) bedrooms, a kitchen/dining room about the same size and possibly even a shared bathroom, say 30 square meters total.
If you are willing to double your commute, you can roughly double the size of your living space for the same money. Triple your commute and you can roughly triple it.
My family lived in a 2 bedroom apartment roughly 45 minutes from central Tokyo, roughly 50 square meters total. As I moved up the corporate ladder, we moved into a 2 bedroom house, 65 square meters, then changed companies and moved into a nice 80 square meter, 3 bedroom company mansion. The same type of living arrangements were available to Japanese employees with similar experience, so it wasn't a gaijin privilege thing.