When people move into expensive housing, they also move out of wherever they used to be living -- often some place cheaper where they lived when their income was lower. Any increase in supply helps.
That doesn't account for all of the people moving into the city from other parts of the State or Country.
Also if they are moving within the city and the previous location is rent controlled, then the landlord will likely raise the rent for the next tenant.
Except San Francisco has a net outward domestic migration now.
This is nothing new BTW. I remember back when training for a marathon in 2001, I had a conference in San Francisco. Dude dropped a duece outside a pay toliet (I guess you tried them for awhile in SF) while I was running at 6am.
From working with homeless people in my state, mental illness is usually a contributing factor. Self-medicating that condition often manifests itself as drug abuse.
