There hasn't been a massive explosion in homelessness in San Francisco. SF's homeless rate hasn't changed much in 15-20 years, it was just as high during the last economic boom in 2005-2006. It was nearly as high on a population ratio basis during the peak of the economy in 2000 as well, despite a lower U6 unemployment rate at that time.

General homelessness was 5,376 in 2000. It was 6,248 in 2005. It was 6,686 in 2015.

SF is doing an extraordinarily poor job of managing its homelessness, despite their affluence and vast resources. That's the fundamental problem.