Actually, I think that in Japan`s case, it has little to do with people not wanting children. If you ask almost ANYONE, they want to have kids. It`s a big cultural thing... The problem is that Japan isn`t really too supportive of having children right now. Raising a child in Japan is *incredibly* expensive. Schooling here is not free, or even cheap, and most children go to university. So whenever you consider having a child, you have to consider the huge amount of money that will have to be spent in raising them to adulthood.
I mean, my son is 2 and we`d love to have another child, but it`s just not financially feasible. Our car is too small to fit two car seats (kids stay in them until around 5), so we`d have to buy another car, etc. And Kindergarten starts from 3 - an average of $300/month around here. And we have to save up for Elementary School entry, etc etc.
And what does the government do to support having children? They give you a percentage of the cost of birth, and a little $50 bonus each month. The government encourages everyone to have more children in words, but does nothing in actions. For example, right now the economy is such that both husband and wife working are not uncommon, and almost necessary for a good life. But everything is geared toward a stay-at-home mother... Which, to be honest, is the ideal for most women in Japan. However, as much as they`d like to stay at home the costs of a child are just too high. So they have no choice but to continue working. There are national daycare centers, but really far and few between compared to the number of children. Some have waiting lists of years. So what happens is that couples decide to wait until they have enough money saved up so that the mom can stay at home after a baby is born. That takes a lot of time... By the time they can afford it, they are too old to have 3 kids.
One or two years worth of savings is one thing, but 5 or 6 along with the costs for school, children`s insurance, etc etc is just too much.
The government REALLY needs to take a look at what parents NEED in order to have more children or things aren`t going to change. Japan still culturally functions on the "big families are good!" principle, so with the proper support people would have more kids. It`s just the support is not there.