If you don't like reading stats, which are readily available, watch the film. But the stats from ideologically neutral sources are telling. A quick summary can be found here, where it says: "..more than 70 countries have (as of mid-2007) a total fertility rate of less than 2" births per woman. Most of those countries are developed countries, where replacement level is 2.1 births per woman. That was three years ago; it's only getting worse. Even China now has a birth rate of 1.75 due to its "one-child-per-family" (!) policy, which, given cultural prejudices, results in gendercide against girls, which feminists don't like to talk about, for reasons I leave to readers.
In all this, there is yet another lesson to be learned about the gulf between ideology and reality. When progs complain of overpopulation, urging that non-procreative sex, of whatever kind and between whatever partners, be the norm, we should ask ourselves whether they are aware of the trends but choose to deny them, or whether they are opposed to population increase only among poor people. For the countries with high birth rates are mostly the poorest countries. The explanatory choices, in other words, are denial and "classism."
One is tempted to prefer the former to the latter. For in general, stupidity is to be preferred to snobbery; and in this case, the former doesn't carry the added disadvantage of hypocrisy. And yet people like Margaret Sanger and Ruth Bader Ginsburg didn't bother concealing their wish that abortion be kept legal as a solution to poverty. When impoverished mothers can easily deny their children the right to live, we'll end up with fewer poor. Right? But that too is a form of denial wrought by ideology. There is no evidence whatsoever that an efficient way to reduce poverty is to try to reduce the number of babies born to poor mothers. But there is a lot of evidence that birth rates vary inversely with the mother's level of education. That is why in developed countries, where women markedly outnumber men among college students and have corresponding career prospects, we see almost catastrophically low birth rates.
Since I'm not a sociologist, I won't attempt a comprehensive explanation for the coming population implosion. What interests me more is why the religious and secular Left haven't caught on to this. I can think of only one explanation: for them, the right to sexual autonomy trumps any and all facts. E. Michael Jones, a classic intellectual crank, once argued that most modern thought can be explained by the desire to rationalize sexual license. I used to think he was just being cranky. Now I'm not so sure.