by Calculated Risk on 8/17/2010 03:30:00 PM

From DataQuick:

A total of 18,946 new and resale homes were sold in Los Angeles, Riverside, San Diego, Ventura, San Bernardino and Orange counties in July. That was down 20.6 percent from 23,871 in June, and down 21.4 percent from 24,104 for July 2009, according to MDA DataQuick of San Diego.

This was the slowest July since 2007, when 17,867 homes were sold, and the second-slowest since July 1995, when 16,225 sold.

Other reports show similar declines as home sales fell sharply all across the country in July. We are now seeing double-digit months of supply nationwide - and we might even see the months of supply metric reach 1 year. The previous months-of-supply high for this downturn was 11.2 months in 2008.

Housing economist Thomas Lawler's preliminary estimate for existing home sales in July is 3.95 million SAAR. If so, this would be fewest sales since 1996. Lawler's estimate for inventory in July was 4.04 million (although it is a bit of a mystery how the NAR calculates inventory). That would mean 12.3 months of supply!

A normal housing market usually has under 6 months of supply. The following graph shows the relationship between supply and house prices (using Case-Shiller).

Click on graph for larger image in new window.

This graph show months of supply and the annualized change in the Case-Shiller Composite 20 house price index.

Below 6 months of supply (blue line) house prices are typically rising (black line).

Above 6 or 7 months of supply, house prices are usually falling. This isn't perfect - it is just a guideline. Over the last year, there have been many programs aimed at supporting house prices, and house prices increased slightly even with higher than normal supply. However those programs have mostly ended.

The dashed red line is the estimate for months of supply in July. Through the roof! And I expect we will see double-digit months-of-supply for a number of months.

This is a key reason why I expect house prices to fall further later this year as measured by the Case-Shiller and CoreLogic repeat sales house price indexes, although I don't expect huge declines like in 2008.