[horatiocain]

There are tons of socioeconomic factors to consider, but I know a lot more fairly average IQ couples with 4 kids instead of two, and I know a lot more smart people who are either childfree or single than parents.

The ability to use birth control properly requires some intelligence.

The needs/career ambitions of a knowledge work career sometimes push aside the desire for a family.

Not trying to be down on people who have lots of kids! There's just tons of factors, some less obvious.

[watwut]

Is it possible that you associate things that correlate with rejection of children with iq? Like ambitions and career - low ambition don't necessary imply stupid. May be that wish for children tamper ambition and career.