The San Francisco housing market has always been a bellwether, and it doesn't look pretty, according to our friends at ZeroHedge.

Tuesday morning, the S&P/Case-Shiller indices showed that San Francisco posted 9% annualized price growth in August, down from its double-digit return of 10.5% in July.

Says ZeroHedge:

At this rate, all else equal, San Francisco home prices will slide into negative territory in another 5-6 months: only the fourth time they have done so in the past two decades.

Click to enlarge

In fact, as the chart demonstrates, there has never been a time when the all important leading indicator that is the San Fran housing market (see here  for the reasons why) has posted such a steep slowdown in annual price increases without a bubble of some sort, be it the dot com, the first housing or the European sovereign debt bubble, having burst.

So: will this time finally be different?