A surprising amount, but of course that's not the only way of impeding construction. See San Francisco's shadow aversion.
New York City is around 15%. Note that Manhattan has among the lowest prevalence of single-family zoning in the US, and a density of almost 70,000 people per square mile.
83% of the Bay Area is zoned single-family and has a density of just 400 people per square mile.
[edit] If you look at NYC-adjacent counties, Bergen, Fairfield, Nassau, and Westchester the numbers get far worse. About 56% of all housing near rail stations in these counties is classified as detached single-family houses. [1]
> About 56% of all housing near rail stations in these counties is classified as detached single-family houses.
That could be totally fine. Many people like living in detached housing and having that near rail service to a major city seems like a good thing.
If the concern is zoning that precludes other uses, that’s a different thing, but a mere observation that X% of housing in some area is of a particular, often very desirable, type isn’t conclusive to me.
If you want public transport to be seen as something everyone uses, it’s probably good that outlying counties like Westchester have detached SFRs in addition to the 44% higher density housing.
If detached single family homes are so popular, you wouldn’t need the government to prevent people from building what they want. Those rules were designed to ensure that certain neighborhoods were only for “the right kind of people”, not because Moses came down from the mountain with a single-family zoning plan.
They are wildly popular. It's not the government preventing people from building what they want (though that's the proximate mechanism).
It's people who live there and voted in the government and advocated for those policies. This is not a government problem, but a people's preferences problem.
You have to consider selection bias here: people live where they can afford to, not necessarily where they’d like. You aren’t seeing what people who were excluded on price or racial lines would want, and you’re not seeing how many people truly want only that style versus not disliking it enough to organize a political movement, since depending on the area that can require things like supermajorities and even nullifying covenants in deeds.
This also hits the tension cities have for balancing the interests of long-term residents against the future. Lots of places have this dynamic now where old retirees block any changes either because they’re opposed to change or fearful of losing the equity which is most of their retirement, but anyone looking at the city finances knows that they need more residents, especially of working age, and that includes lower income families if you want to be able to have service workers, city employees, etc. actually live there. This is especially true in places like California where old residents pay far less in taxes but have equally high, if not higher, expectations for city services.
