So it looks like the inventory collapse is real. All three of my sources are showing equivalent, sudden declines. Some market color I've gathered in the last couple of weeks: both the brokers and agents I've spoken to feel prices are trying to rebound, but that appraisers are reluctant to assess much above the recent lows so soon. This means that both the banks (REO) and regular sellers are holding back waiting for more favorable comparables before listing for sale.
Seeing as this selling season is almost over, a lot of sellers are waiting until Spring 2013 before testing the waters again. Of course, to the degree that any market price support is due to sub 4% interest rates remains to be seen as well. I am holding to my hypothesis that the low occurred between 2010 and 2011 in Sacramento, and we've begun a slow, bumpy rise in prices that will last for at least two years. Since housing in Sac (and all of California) has been in a recurring bubble cycle for decades, maybe we'll return to the madness by 2020, just in time for those Millennials to become credit-worthy. :)
Four County Inventory Levels
Inventory on 2012-08-18: 3875