http://www.youtube.com/watch?v=Qrg8t34yXRs
It was only a few years ago I was on the other side of this debate. Well, actually, as I recall my position it was that poor people were still having too many babies while the affluent (and presumably the more intelligent, or at least the most in a position to master higher tech and math) were having too few to even replace themselves.
I've also, since then, come to the grudging conclusion that much of the lack of children in 1st world countries is, actually, a combination of (1) social/governmental self-immolation (2) mental illness and (3) chemical castration. Put differently: (1) propaganda and social collapse (2) queer people are genetically dead, and - with some exceptions. (legitimate, genetic gays) - mentally ill (3) we are bathing ourselves, and our children, in endocrine disruptors and other toxins...chemically castrating them.
Thought I would post this link to a Jordan Peterson interview on this broad topic of population collapse in the most advanced countries.