> limited supply side market.
Just to keep up with the national US growth rate (0.7%), San Francisco alone would need to make housing for almost 6000 new residents per year. In the first decade of this century (2000-2009) there was a total of 2,500 added per year, or roughly a half of what's needed, and that's a simplistic calculation for what's needed.
Add in a renewed popularity of cities and urban living over the suburbs, and it's no wonder then, that housing is in short supply in San Francisco.
The reality that San Francisco doesn't want to face is that housing for at least 6000 people needs to be added EVERY SINGLE YEAR, just to keep up. All the challenges related to adding housing in San Francisco (here's a hint; a 150-year old facade isn't historic) add up to one thing - very limited supply, and any Econ 101 student could tell you the result. What happens when demand rises while supply stays the same (or even goes down, relatively)? Prices skyrocket.