Well, there are definitely social changes. For one, after WWII, Japan had a massive "baby boomer" effect, many of the servicemen who came back to Japan from our former colonies -- eventually "went to town", as the Americans would say it. lol. It was common for post-war Japanese families to have as much as 4-7 children per couple.
Back then it was common to marry at such a young age of around 18, 20, 22 et al.
Nowadays, society is placing more emphasis on education. More kids are going to graduate school, developing their careers before marrying and producing offspring. And when they do, it is around 1 to 2 children (ideal), instead of say 4 or 7 (tho it is still common in rural parts of the country).
Sustaining 4-7 kids takes a lot of capital. Imagine having to take care of 5 crawling babies in the living room!? LOL.
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What i mean is -- becoming active participants of Japanese Society. We should bring in more immigrants who are open to the idea of "becoming" Japanese. Once an immigrant chooses to naturalize, he or she must give up their former citizenship and nationality. They then becoming Japanese Nationals. Their loyalty and dedication should be to their New Homeland-- Japan. And to no other.