It seems hard to extrapolate a long-term boom-bust cycle from those graphs. SF may be more sensitive to national trends, but I only see two clear busts, and one

It seems hard to extrapolate a long-term boom-bust cycle from those graphs. SF may be more sensitive to national trends, but I only see two clear busts, and one was 2008, during which housing markets collapsed almost everywhere. The earlier one coincides with the 2001 downturn and dot-com bust. You'd probably see echoes of those busts in plenty of other housing markets.