New York City is vast. Brooklyn alone is 40% larger than San Francisco.

If you're talking about outlying areas, the rest of the bay area is amazingly not dense given how expensive housing is.

You can't really compare a single municipality to several that collectively equal it's size. The latter case has a whole lot of more localized and conflicting political interests that serve to hold back the area as a whole.

Note New York City has less of these issues because over the centuries it gained control of its neighboring areas from other counties, something San Francisco never did.

But given how fervently anti-development San Francisco itself also is, would it even have helped?

San Francisco looks positively pro-development compared to places like Palo Alto. At least they allow townhomes, not requiring detached houses with large lots. If more of the Peninsula were even near SF levels of density, the housing issues would be a lot less severe.

I know they're different politically - I'm comparing the results, which are terrible.

Or look at Hong Kong and Singapore.

That's twice you've said that, care to elaborate?

Hong Kong 6,544/km2 17,024/sq mi

Singapore: 7,697/km2 19,910/sq mi

Hong Kong is 75% rural montane forests. The city density is closer to 80000/mi^2.

An unsurprising choice, since for a century residents were surrounded by a much poorer, much more dangerous country, and the ocean, in all directions. The only place you can go in Hong Kong to escape are its parks.

Those numbers are the population densities for the whole countries. I wasn't able to find densities for the urban areas of Hong Kong or Singapore.

Btw, Monaco is at 48 462 people per mi2.

Singapore is reasonably dense as a whole for around 5 million people.

If you look at the high numbers for Barcelona, Hamburg or Paris, that's only the urban core. Singapore, of course, also has a denser core.

(And what scythe said about Hong Kong.)