It might be one of the causes, but it's sort of naive to consider it as the main one. SF is not the only big city with a major influx of people coming there fo

It might be one of the causes, but it's sort of naive to consider it as the main one. SF is not the only big city with a major influx of people coming there for work, I have seen quite a few European and American major cities, but "armies" of homeless out in the open like in SF I really haven't seen anywhere else. It's probably a mix of causes, not least the very mild climate, if I were homeless I would rather spend a winter on the streets of SF rather than in Boston or NYC, or a summer in Houston...