Prices fell from 1989-1994. About 10-15% in nominal terms, more factoring inflation of course. Some areas were hurt more than others, Silicon Valley in particular. In Cupertino, where Apple is based, it was a dark period.
SF itself was probably closer to the 10% mark, but decline it did. It also fell in the 1981-1982 recession (in real terms), which everyone seems to forget about, as well as 1972-74. The idea that SF prices never drop is a myth, pure and simple.
Judging from today’s nosebleed prices in the city by the bay that lesson will have to be relearned yet again, and more painfully than ever it seems.