[The Demographic Transition is a theory where demographers] believed was fertility rates decline from being in the 6 or 7 range, which is what they had been in the 1800s, and that they would then settle another replacement rate because they thought that what people naturally would want…what everybody would naturally want was two children and would settle into a replacement-rate society.
Well the problem is as fertility rates began shrinking they didn’t stop at 2, and so anywhere where fertility decline has set in, it never stops at the replacement rate. It always continues diving towards the floor and heading down towards 1.4 or 1.5.
And that became the question: So why are we stuck in dramatically sub-replacement-rate fertility? And the theory which was put forward to explain that was called then the theory of the second demographic transition. And what those guys argued … very persuasively that the reason people didn’t stop at two was because once they mastered contraception, once they had conquered infant mortality, once they had access to food and higher standards of living and medicine and could do whatever they want—conceive of themselves however they want—they would change their worldview.
They would no longer really see themselves as standing in a long line of people paying sort of fealty to the past and looking forward into the future. They would see themselves in their own self-actualization, the highest form of human existence, and this would then cause them to have fewer and fewer and fewer children.