[jaclaz]

Maybe that would account for a part (I am also not at all an expert in California, so it is just speculation), but those cannot reasonably account for 40% of workers.

I mean, if you live in SF and have a yearly income of "only" 50-60,000 US$ working some 2000 hours at 25-30 $/hour, and you live in a house that you can rent for roughly the same amount or that you can sell for (say) a million, what actually keeps you there?

Maybe you can find somewhere else a similar job, paid in the 15-20 $/hour range, you lose 20,000 on the job but get an additional 40,000 from the rent or from interests on the capital.