What is causing the demographic winter of the west?

The western world faces a "demographic winter" with birthrates falling below population replacement numbers in most western countries. The consequences of a falling birthrate will be particularly significant for countries as their population ages. In Canada, as baby boomers retire there will be fewer and fewer working people to pick up the health care and pension costs plus service the national debt. If we think our current financial crisis is bad - imagine one where the government collapses because there is not a sufficient working population base to pay for the needs of an aging society.

I remember being teasingly chided by a single woman when I was pregnant with my sixth child and I reminded her that when she was lying in her hospital bed it would be my children that were paying for her medical care. But all joking aside - who does she think is going to be paying the taxes that will support her medical care and her government pension costs? The idea probably never occurred to her as she pursued her career.

The idea that children are an obstacle to a woman "fulfilling" herself is pervasive in this society. Every year we see the usual article in the paper outlining how much it costs to take a child from birth to a university education - and we never consider how much that person enriches the lives of their family, the common good of society or even on a purely pragmatic note - how much tax revenue that individual will generate over the course of their working life. It seems to me that having a child in western society and in particular having more than two children seems to require an immense amount of courage.