> If their population began declining twice as fast as now (1% per year) it would take around 105 years for the Japanese population to reach the level it was at back in 1900.

As the population declines, the rate will pick up. A nearly extinct Japan will give rise to an even more profound nihilism.

> A lot of things can happen in this time frame.

Tell us the science fiction story where the Japanese learn to love life and want even more Japanese people to exist to revel in it.

Nothing happens in that time. It's extinction. Their culture isn't nearly malleable enough for anything significant to change.

> the rate will pick up

Why?

> Tell us the science fiction story where the Japanese learn to love life and want even more Japanese people to exist to revel in it.

Could someone just 60 years ago easily predicted the current situation? Possibly but it would have been a contrarian opinion.

What about 100 years ago? 150? 200? Almost impossible.

See the pattern?

> Their culture isn't nearly malleable enough for anything significant to change.

Right.. I'm sure there were people who were saying this in the 1860s or 1940s. Turns out the Japanese society was one of the most malleable ones that ever existed. Of course there is no guarantee that might happen again. Who knows... I'm not the one pretending I know everything.

> Why?

Because the fertility that they see expressed around them by adults acts as the ceiling, not the floor for their own future fertility. If grandpa had 3 and mom had 3, you might only have 1 or 2, you'll very rarely ever have 4 of your own.

This is just the nature of those numbers... a person with 2 kids is, theoretically, working on a third. Until they get too old, and then it's an "oops".

So, it ratchets downward. When someone waits too long and has fewer, then they become the normal that children around them see, those children internalize the new number (or at least some sort of fuzzy average of those adults around them).

One would expect that to decline ever faster. And that's in fact what we see so far... instead of a fertility rate of 1.4 that just holds steady for centuries until extinction, it drops year to year and decade to decade, and will take far less than a millennium.

> Could someone just 60 years ago easily predicted the current situation?

Probably, if they somehow could have shed their 1960s biases. The trend had already started.

> Turns out the Japanese society was one of the most malleable ones that ever existed.

It's not malleable at all. Adaptable is one thing. Adaptation is an active verb, each person individually and all collectively will themselves to change, so to speak, to overcome challenges. They do that occasionally.

Malleability suggests that some outside force can come along and change them against their will, or at least without them noticing... and they are less malleable than many other cultures. If they were malleable, then we'd expect far more results from the various programs that the government puts in place to alter their culture. And those programs have fallen flat on their faces. They don't make a dent in Japanese work culture, they won't make a dent in Japanese fertility.

We're probably only 25 years or less away from 0.3 fertility rate. By about that time, it won't be so easy to argue against those who say what I'm saying... so those who did will have moved on to "this is a good thing". Some are already hinting it in the other replies. They hate humans, they wish they never existed, and they are secretly cheering this on. (Yet, I'm the fascist somehow.)

This would make me sad, except that it's difficult to be too upset about people who wish they never existed making themselves extinct.