When people are free to decide how many children they want, this amounts to 0, 1 or 2 typically. Which averages out to about 1.5-1.8 in most developed nations,

When people are free to decide how many children they want, this amounts to 0, 1 or 2 typically. Which averages out to about 1.5-1.8 in most developed nations, which is significantly below replacement rate. Japan is an extreme case. People often blame the cost of living. Whilst it doesn't help, it's not the root cause. The root cause is straightforward: people simply do not WANT more children. Those that want children, will often have 2. There's very little reason to have 3, 4, 5 or more once you have 2. Two children already dominate your life so there's little incentive to just let the number grow arbitrarily. And having more than 2 children has very real consequences. For your home, your car, your schedule, your sanity. Even most millionaires will not have a huge amount of children. Bottom line: most people still want children and will have 2. Which is not enough to cover the replacement rate. No policy, monetary or otherwise, will significantly move the needle. Japan's issue is the above universal behavior combined with additional local constraints. As also seen in South Korea and China, the "work yourself to death culture whilst also financially supporting your ageing parents" means your culture as a whole ultimately goes extinct. It makes family formation near-impossible. Instead of working more we should work less if we're interested in continued existence. The world won't move in that direction though it's "all hands on board" to deal with the current ageing society. Mass immigration doesn't solve this. It's a brain drain for those countries, but also consider that a giant population of young people will turn into a giant population of old people, requiring even more young people. Which won't happen because also in developing countries the birth rate is in decline. A very dark conclusion you could make is that people get too old.