And what does this mean for aspiring do-gooders? (Work in progress.)

The puzzle

If you care about having a lot of impact, should you have kids? Naively, it seems like having kids would be bad for impact & career success. Kids take up time, energy, focus, all of which could be directed towards working harder.

But in the last few years there’s been a bumper crop of babies, among a bunch of people I respect for their work:

Scott Alexander & Megan
Holden Karnofsky & Daniela Amodei
Paul Christiano & Ajeya Cotra
Sam Altman & Oliver Mulherin

And many other figures I look up to, have had kids for a while:

Bill Gates & Melinda Gates
Paul Graham & Jessica Livingston
Dustin Moskovitz & Cari Tuna (?)
Elon Musk

Then, zooming out to some reference classes of successful people:

Billionaires. On the Forbes list, the top 25 (as of June 2025) all have children.
US Presidents. It’s been more than 100 years since a president didn’t have children.

So: if having kids is bad for impact, how come all the most successful and impactful people do so anyways?

Some ways to reconcile this?

Maybe this was a “selfish” choice, and in a counterfactual world where they didn’t have kids, they could have done even more good in the world
Maybe success leads to having the resources to have kids, because kids are a desirable consumption good; but it’s not that having kids leads to success.
Maybe the base rate of people having kids is pretty high anyways (~80% in 40 year-olds)
Maybe these figures are primarily men, and their wives are the ones bearing more of the cost

But none of these are that satisfying to me:

I think this would predict the existence of some mega-impactful individuals who deliberately chose not to have kids, and cite that as the reason for their success?
At a glance, it looks like the billionaires have earned most of their money after having kids. They were probably already pretty well off before, monetarily — but also in situations where they were extremely busy (average age of 32, so in the prime of their careers).
I’m no statistician but it feels like the rate of having kids among “successful people” is statistically significantly higher than the baseline of ~80%. At the very least, the baselines seem similar
It is the case that among the most impactful women I know, some have kids (Ajeya Cotra, Sheryl Sandberg) while others (Beth Barnes, Cate Hall, Katja Grace) are childless, and the childless rate seems higher than among impactful men.

Instead, I suspect that having kids may just be good for impact.

Applying (or misapplying?) functional decision theory

Functional Decision Theory says that you should choose the function that leads to the best results. It argues for one-boxing in Newcomb’s Paradox, that is, walk away from a guaranteed visible $1000 so that you end up with the $1m in the hidden box.

Newcomb’s Paradox is usually explained using premises that border on supernatural (”Omega, the perfect predictor”); here’s a variant that I find more relatable: you’ve just watched Alice, a very smart human, make the right prediction in 10 out of the last 10 cases.

I suspect something similar is at play on the question of kids & impact. While a CDT mindset might say something like “having kids is costly, thus it’s rational to not do so”, the FDT mindset observes “huh, all the successful people are having kids. What am I missing?”

Why might having kids could lead to more impact?

Useful goalposts: Maybe having kids is a forcing function to get your life in order, so that you have the resources to support them
Focus: Maybe after having kids, you are forced to prioritize your time and attention on the things that matter most, and this focus is actually better than the alternative of having marginal infinite time and no demands on your attention
Skilling up: Maybe something about taking care of kids teaches you a skillset that is broadly applicable to other domains of life, eg how to lead people, how to manage time
wellbeing/mental health/instrumental time off: Maybe having kids makes people happier which helps with the rest of the impact thing, “having a grounding force that keeps you sane”, stabilizing
Networking: Maybe the “parents network” is actually really important — because other great people also have kids, and sharing playdates, daycares, advice, schools is better than going to yet another party full of early-career 20-somethings

I notice that these don’t add up to enough to overcome the time/energy/focus cost of kids — which is to say, I think these are part of the answer but there’s still something mysterious going on.

(The networking piece seems the most plausible for me personally; my daughter has provided a good excuse to spend more time with some really amazing and impactful folks.)

Unfinished

When do high-impact people first decide to have kids?

Scott Alexander: ~35
Holden Karnofsky: ~40
Sam Altman: ~40
Paul Christiano: ~34
Bill Gates: ~40
Elon Musk: ~31
Mark Zuckerberg: ~31
Jeff Bezos: ~35

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Billionaires: Out of top 10, average age of ~32, per Claude:

Does what field you’re in matter for this?

Tentatively, it looks like leaders are the ones who are most likely to have kids.

The case against

Looking at Manifest 2025 speakers… It does seem like many more of them are childless. They also seem on the younger side, though.
Childless historical great people