There is a convergence of reasons, and Japan is only ahead of the curve. People who have been raised as a single child are unlikely to have more than one child

There is a convergence of reasons, and Japan is only ahead of the curve. People who have been raised as a single child are unlikely to have more than one children, this is simple pattern reproduction. The cost issue is mostly related to cost of space, with today standards we need one more room per child, not everyone can afford that. Culturally, the pressure on girls and young women has relaxed tremendously, education and financial freedom have a very measurable effect on natality. Overall, I don't think this is a bad thing. We can adapt. Also, population is a huge variable in energy/resources/pollution.