[nonameiguess]

That seems to be missing that many of those highly-paid professionals were not highly paid in their peak fertile years. Engineers maybe, but doctors and lawyers tend to spend many years in school and then interning. If you start having kids at 30, you'll usually end up with fewer total kids than if you had started at 20. The most highly paid engineers are likely those willing and able to relocate frequently, too, which brings its own challenges. Money is needed to feel secure enough to start a family, but so are stable living arrangements and social structures.

[bpodgursky]

Having known many people who went through medical school and residency, I'm confident almost none of them would have accelerated their family plans with more money. Medical residents who work 80 hour weeks simply have less than 0 time to start a family.

(And in fact, of the very few who did, it is always when the husband was a resident and the wife stay-at-home or a different career. In these cases, the finances were not a huge constraint; if nothing else, it is extremely easy to take on cheap debt as a resident.)

I can't speak as confidently to lawyers and interning, but I'd be surprised if the dynamic was different.

[giantg2]

Even if starting at 30, that doesn't explain it being < 2. There are medical interventions on both sides of the equation (birth controls and fertility treatments). Preferences are the main drivers in my opinion.