The root cause is way too little development relative to demand, orchestrated via zoning regulations. Wikipedia spells this out in detail for San Francisco [1].
> Since the 1960s, San Francisco and the surrounding Bay Area have enacted strict zoning regulations. Among other restrictions, San Francisco does not allow buildings over 40 feet tall in most of the city, and has passed laws making it easier for neighbors to block developments. Partly as a result of these codes, from 2007 to 2014, the Bay Area issued building permits for only half the number of needed houses, based on the area's population growth. At the same time, there has been rapid economic growth of the high tech industry in San Francisco and nearby Silicon Valley, which has created hundreds of thousands of new jobs.
(Supply Price goes up.
If we're to solve the housing affordability crisis, city councils simply need to drop onerous zoning regulations and permit construction such that supply can meet demand.
Anything short of this is just a beat-around-the-bush bandaid that hasn't and won't achieve anything. For instance, rent control. What a regressive concept, with tons of unintended consequences.
[edit] for real do you think there'd be a housing shortage or affordability crisis if the entire southern and western 3/4 of San Francisco was allowed to build up from 4 stories to 6? Basically everything other than districts 3 and 6. [2] That'd easily add 50% more housing.
[1] https://en.wikipedia.org/wiki/San_Francisco_housing_shortage
[2] https://voterguide.sfelections.org/en/san-francisco’s-superv...