[TeMPOraL]

Ok, I think I should have written "international scale", I apologize for the confusion.

I don't know of any study on national level, i.e. of families in a single country. The only thing I know of are anecdotes and stories about very poor families having 5+ children.

[Retric]

I have seen this stat from a few studies.

EX: http://econlog.econlib.org/archives/2011/06/kids_are_normal....

Higher income > more kids, Higher education > fewer children.

This seems fairly obvious as people are less likely to have children and stay in school. But, as I understand it the effect is larger than that.

[MSM]

I have heard the opposite from many studies as well. You linked a post that spawned many, many rebuttals by various organizations.

http://economix.blogs.nytimes.com/2011/07/01/richer-people-w...

http://freakonomics.com/2011/06/10/the-rich-vs-poor-debate-a...

[Retric]

Both of those ignore the education factor.

Basically if you have two groups of American born, collage educated men, with of the same age then income positively correlates with number of children. But, if you compare collage dropouts vs. people that have PHD's then the PHD population makes more money and has fewer kids. So, education is a huge confounding factor.

We went from 14 being a reasonable age to start a family to 24 or even 34 being the 'reasonable age' that's a huge impact. But, ‘wealth’ as an independent factor aka adjusted for age, education, country etc becomes a positive factor.

PS: Historically, starvation also limited family size.