There is an interesting article by Tom Bethell in the American Spectator about the demographic suicide the wealthy nations are currently committing. An excerpt:
I believe that two interacting factors shape population growth or decline: economic prosperity and belief in God. As to the first, there is no doubt that rising material prosperity discourages additional children. Fewer infants die; large families are no longer needed to support older parents. The welfare state—which only rich countries can afford—has greatly compounded this effect. When people believe that the government will take care of them, pay their pensions and treat their maladies, children do seem less essential.
A rise in prosperity also encourages people to think that they can dispense with God. Religion diminishes when wealth increases—that’s my theory. But with a twist that I shall come to. Wealth generates independence, including independence from God, or (if you will) Providence. God is gradually forgotten, then assumed not to exist. This will tend to drive childbearing down even further. Hedonism will become predominant. Remember, Jesus warned that it’s the rich, not the poor, who are at spiritual hazard.
The Bible consistently warns about the dangers of money, and we can see a primary reason for these warnings in the actions of modern man. Those who are best able to provide for children – the wealthy – are the least likely to want to actually have children. Money breeds selfishness, and the more money one has, the more likely he is to put his own comfort and desires above all else, thus killing the desire to care for others. In the end, this leads to cultural suicide.