I strongly doubt that. It was quite common in western Europe too. My parents got married in 1970 and did briefly live with my grandparents (who had a gigantic h

I strongly doubt that. It was quite common in western Europe too. My parents got married in 1970 and did briefly live with my grandparents (who had a gigantic house that was still dirt cheap when they got married directly after WW2), but moved out soon after that. As far as I know, people moved out either when they married, or when they went to a university in a different city. Around 1990 I knew one guy who had a job and still lived with his parents, and I thought that was odd (he spent all his money on fancy audiophile equipment).