Having hit an 8-year seasonal high last week, the number of homes on the market in San Francisco has ticked up to 980, which is 6 percent higher than at the same time last year and the highest inventory level in the absolute since the fourth quarter of 2011.

That being said, the year-over-year gain is currently being driven by listings for condos (660), which are up 15 percent, year-over-year, not including the vast majority of new construction condos for sale across the city, versus single-family homes (320), which are currently down 10 percent, year-over-year.

Expect inventory levels to continue to climb through October, especially if the year-to-date trend in San Francisco home sales holds.

And while the market for condos is certainly more volatile, with higher highs and lower lows, keep in mind that it remains a leading indicator for the market as a whole.