The New York Times hits on one of the underappreciated potential costs of stupid zoning rules: expensive housing means fewer kids. People either don't have them, have fewer, or move away to have them.
A few generations ago, before the technology boom transformed San Francisco and sent housing costs soaring, the city was alive with children and families. Today it has the lowest percentage of children of any of the largest 100 cities in America, according to census data, causing some here to raise an alarm.The death spiral mechanics aren't hard to imagine. Families move out as the place gets too expensive, and the first to go will be single income families who shoulder most of the social capital burden in keeping the schools going. School quality slips, making others go. The place is too expensive for teachers to live, so the good ones ship out too.
Prohibitive housing costs are not the only reason there are relatively few children. A public school system of uneven quality, the attractiveness of the less-foggy suburbs to families, and the large number of gay men and women, many of them childless, have all played roles in the decline in the number of children, which began with white flight from the city in the 1970s. The tech boom now reinforces the notion that San Francisco is a place for the young, single and rich.
Auckland could risk heading that way too. It's already hard for the schools to hire teachers because of housing costs.
I will note though that I've not seen any studies looking rigorously at housing costs and natality. Not that existing studies aren't rigourous; I just don't know that literature.