Per the studies that I have seen over on Fertility Twitter, none of them seem to really make much of a difference.

Right now they are on a meme where they want to turn large tracts of national parks into suburban developments because some study said that apartments are bad for families. I ... its ... yeah...

All the studies seem to contradict, meaning that likely they are having little to no measurable effects.

'Yeah, we just need to try harder though'.

I mean, yeah, we're mostly trying to exhaust those 80-20 effects right now and see if anything sticks. From the little I have seen: nope. It's the proper way to look at it. Go for the cheap stuff with big effects, then see.

But you're right, it may be more like a 99-100 thing, where you kinda have to get it all right before it kicks off. We don't seem to know right now and are still exploring the space.