Than you for catching the typo. Also I find it refreshingly honest that you acknowledge reality of this.

I'm not sure the Moldbuggian taxonomy carves reality at the joints but I have no problem employing it as needed.

The class produces its fair share of mathematicians. In absolute numbers I'd say more than the upper classes.

I doubt it (IQ, heredity), unless you're including Asian immigrant populations. But in any case mathematicians usually spend a good amount of time in university which means, wherever they grew up, by the time they're looking for jobs they're usually firmly entrenched in a brahmin social circle.