I would propose more supply be built on the land owned by developers who want to build more supply.
For reference, the street view below is the heart of the Mission. Unfortunately, most people here would rather preserve the slums than build enough housing to support a diverse bunch of people.
Permits, height laws, comment periods where some nimby will block the development. Otherwise they would of done it already because there is a lot of relative cash to be made to the cost of building.
On a relative per capita basis, SF is building a lot less than lets say houston or similar. And the reason why it's a lot slower is because of all of the above.
It's a chicken and egg situation. Developers propose larger than they want because inevitably the negotiations with city and neighbors reduce their plans.
Even Paris, a city that has banned high-rises, has a population density about 2.5x that of San Francisco. I realize SF doesn't want Miami-style condo towers everywhere, but there's a lot of room to densify just by putting in more mid-rise buildings in the 5-6 story range, rather than having so much of the city be low-rise.
Which would typically require demolition of existing structures. Most property owners don't have the capital to destroy their current structures just to replace them with taller buildings. It would also require displacing current residents, who won't have anywhere else to live while the new building is constructed.
In SF, when a lease "expires" it converts to an indefinite lease with a 30-day notice from the tenant to terminate. The lessor may only terminate for just-cause with varying notice periods and possible compensation to the lessee for damages caused.
Landlords push people out of housing in SF every day. It's often under shameful circumstances. And its not just Ellis Act, though that's a big part of it.
SF companies trying to hire people. Anyone in SF who would like to derive the benefit of the labor of low wage earners (teachers, nannies, chefs, etc).
And the people who would like their pensions to be fully funded due to investment gains from new tech companies in SF, currently hindered by rent. And people who want to use exciting new products built by SF companies which are limited or don't happen due to lack of office space. It's a drag on not only the city but the state, nation, and world.
"But for the tight limits on construction in California’s Bay Area, they reckon, employment there would be about five times larger than it is. In work that has yet to be published they tot up similar distortions across the whole economy from 1964 on and find that American GDP in 2009 was as much as 13.5% lower than it otherwise could have been. At current levels of output that is a cost of more than $2 trillion a year, or nearly $10,000 per person."
Sorry, I meant housing, which raises base salaries, which makes it hard to do a bootstrapped startup (both one's own living expenses, and hiring first 20 employees requiring market salary to survive)
If you could live comfortably in SF on $30k/yr like you can in a lot of college towns, you'd be able to bootstrap a company for a couple years on just your savings, which would increase the variation in startups -- you could see more genuinely ambitious startups which didn't depend on getting funded.
I suppose we could start landfilling part of the bay a la Boston.
[0] https://www.google.com/maps/place/San+Francisco,+CA/@37.7738...