The vertical axis shows the annualized default rate for the three month period ending in August, for each of the nine Bay Area counties. The horizontal axis shows the percentage change in price through May, measured relative to the three-year period from July 2005 to June 2008 (i.e., the bubble years).Note: I reversed the horizontal axis to make the chart easier to read. Ideally, it would show the percentage of homes that are underwater. I don’t have detailed data on underwater homes, however, so I used the change in price relative to the bubble years as a proxy for the percentage of homes that are underwater. You can read more about this proxy for underwater homes here and here.
The relationship between the two variables is clearly strong, and supports the idea that underwater homeowners are making cold-blooded decisions to default, simply because they believe it’s in their interest to do so.
On the other side of the coin, there seems to be a widespread belief that heavy foreclosure activity depresses sale prices. If that’s true, then falling prices can lead to a self-reinforcing “doom loop” where underwater homeowners walk away from their homes, which then hit the market as foreclosures and depress prices even further.
Perhaps that story holds true in other markets, but there isn’t much support for it here in the Bay Area. Take a look at the chart, below, which compares recent price changes to REO sale activity for the nine Bay Area counties.
The vertical axis shows the change in median price over the last twelve months. The horizontal axis shows the number of bank-owned homes (REO’s) that have been sold during the same period.REO’s accounted for more than 30% of all sales in five of the nine Bay Area counties. All but one of these counties outperformed San Francisco, where REO’s accounted for only 15% of sales. I wouldn’t call this an ironclad case but I don’t think Bay Area homeowners need to worry about foreclosures depressing property values.
I’ve updated my October 2008 chart through July of 2010. The chart compares the beginning-of-year inventory of single family homes in California to the change in median real price during that same year. As you can see, with the notable exception of 2008 and to a lesser extent, 2007, the beginning-of-year inventory has been a very good predictor of subsequent price movements.
The chart comes from 
The current recession is unusual because it was brought on by falling home prices. Financial institutions and households both were highly leveraged at the peak of the housing market. As a result, their balance sheets suffered serious damage when home prices fell. Economic demand naturally fell, leading to the current recession. (As you can see from the chart, home prices began falling rapidly before unemployment started climbing. That's consistent with the idea that falling home prices caused the recession.)
Sales in the west region came in at 44,000 units in July, on a seasonally adjusted annual basis. That's also a record low, going back to 1973. Sales had been improving until the end of April, when the home buyer tax credit expired.
Evidently, builders' hopes were buoyed by tax-credit-induced sales. Did they not see the end of the tax credit coming?
Sales had been rising rapidly as the April 30 expiration date for the home buyer tax credit approached. The subsequent drop-off in sales was therefore widely anticipated. (The same pattern was observed with the original home buyer tax credit, which expired on November 30, 2009.) Still, the scale of the decline came as a surprise. In a survey of economists by Bloomberg News, nobody had predicted such a large decline.
Housing is far more expensive in San Francisco than in other parts of the country. Consequently, the tax credit might have been expected to have a relatively small impact on demand. Surprisingly, however, home sales fell almost as much in the City as they did in other regions. Between June and July of 2010, home sales fell roughly 21% in San Francisco. The July 2010 total (452 units) was 17% lower than the corresponding figure for July 2009 (543 units).