Well personal space and personal time were not in abundant supply in our times of growth. It is true that urban areas have far fewer children than rural areas and that this is a worldwide property. It’s a pity since I like the ability for kids to walk to places and take the bus or train and I’ve grown up in a rural place (pythons and peacocks, cows and birds, scorpions and cobras!) and in a highly urbanized environment and they both have their advantages.

I personally think it’s just opportunity cost. Children seem like a big deal with unclear benefit and so as people get the chance to substitute with other things they do so. For my part, we put a lot of work into having kids and we live in SF. If we leave, it’ll be because my daughters don’t have mobility here because crime and cars impede their independent movement.

> I personally think it’s just opportunity cost.

Nope. It's just time and personal living space. It's THAT simple.

Go on, try to plan your day with transit and no car if you have 3 children (with 2-3 year age gaps). You'll find that this really works only if everything is concentrated, or if it's a full-time job for you. That's why we hear so much about "15-minute neighborhoods".

But when everything is concentrated, it becomes EXPENSIVE and you also lose any semblance of choice. You will likely have only one school, one daycare, one community center. You become hemmed in within that "walkable" neighborhood. That park nearby? It surely can look nice, but what if it's the only park within reasonable walking distance? So you don't even have an _option_ to go somewhere else with kids, without making it a full-day trip?

People like to laugh at Texas, about how riding an SUV to a walkable park is ridiculous. But is it, really?

The way to fix all of it? Suburbs and cars. Cars provide personal freedom and personal space. That's also why the US had a higher birth rate for much longer than Europe, and it started cratering once young people were forced (by the economy) to move into dense city cores.