I doubt it's the unofficial 11 hour work day cause that's not uncommon in the United States either.

Europe has the exact same problem of declining birth rates. France has a government mandated 35 hour work week and they are experiencing a similar decline as well.

The US has declining birth rates as well but not so rapidly as Europe or Japan. Some speculate it has to do with the tax burden of each country. As each family has less money left there is less of an incentive to have more kids.

The AVERAGE Japanese man leaves home around 7am and comes home at 9pm or later every weeknight. Sure some men in the USA and other countries work this kind of schedule, but it's the exception. In general, Japanese men don't have time to do ANYTHING with their families on most weekdays. Men in the USA still have dinner with at home, coach soccer on weekdays, have time to watch a movie with their wives, etc. I know that many in the USA are working long hours compared to most countries, but it's not comparable in my opinion. Japanese workers are in a league of their own.

As for the correlation with the declining birth rate, I admit that's speculation, not an objective statement. But many Japanese women are expressing in survey after survey that that they don't want to ever get married or have children. People are obviously concerned about that trend increasing.

The root cause of the declining birth rate in, Europe, Japan, and the US (read all wealthy industrialized countries) is quite simply one of the seven deadly sins: GREED. Let me use the US as an example. People are unwilling to make the necessary sacrifices that raising a child means so they use birth-control or abortion. I do not for one minute think that they are having less sex. As a result of this the US needs foreign workers (read pseudo-slaves) to replace the lack of native children. In it is the GREED of the American businesses and the American consumer which causes them to export jobs to pseudo-slaves in China. Just as it was GREED in the 1700's which cause white Americans to import slaves to America in those times. When will countries wake up and make decisions based on what is right for the country in the long term and not what satisfies our short term desires.

The root cause of the declining birth rate in, Europe, Japan, and the US (read all wealthy industrialized countries) is quite simply one of the seven deadly sins: GREED. Let me use the US as an example. People are unwilling to make the necessary sacrifices that raising a child means so they use birth-control or abortion. I do not for one minute think that they are having less sex. As a result of this the US needs foreign workers (read pseudo-slaves) to replace the lack of native children. It is the GREED of the American businesses and the American consumer which causes them to export jobs to pseudo-slaves in China. Just as it was GREED in the 1700's which cause white Americans to import slaves to America in those times. When will countries wake up and make decisions based on what is right for the country in the long term and not what satisfies our short term desires? What we need is a renewed spirit of sacrifice and unselfishness, otherwise we can witness the end of our culture. (P.S. The problem Europe has with Muslim radicals can be traced to the same source as in the US)

In Japan men ARE having less sex. At least they are not having much sex at all with their wives. This is not a glib comment but pretty objective. I can't cite a source right now, but I can say this is pretty commonly known here. In fact, I've seen quite a number of commentators on TV saying that men aren't having sex with their wives because they work too much. Obviously, the root causes of sexless marriage run deeper than mere work habits, and I don't disagree that greed is a root source of many problems here and elsewhere. Sorry my thoughts in this comment are so unorganized.