by Calculated Risk on 6/22/2010 07:28:00 PM

Earlier I posted a graph showing the relationship of existing home months-of-supply to house prices. When months-of-supply is below 6 months, house prices are typically rising - and above 6 months-of-supply, house prices are usually falling (this isn't perfect, but it is a general guide).

So how high will months-of-supply rise this summer?

Here are some estimates of sales via James Haggerty at the WSJ: Outlook for Home Prices Grows Darker

Since April 30, new purchase contracts have plunged ... Lawrence Yun, chief economist for the Realtors, estimated that contracts signed in May were 10% to 15% below the weak level of a year earlier.

Ronald Peltier, chief executive officer of HomeServices of America Inc., which owns real estate brokers in 21 states, said new home-purchase contracts in May and June so far are down about 20% from a year earlier.

Contracts signed in May and June lead to sales later in the summer (counted when escrow closes).

Sales in July 2009 were at a 5.14 million rate (SAAR). Usually inventory increases in July, but if we assume inventory is steady at 3.892 million, the following table shows the month-of-supply estimates based on three year-over-year declines sales in July 2009:

Sales Decline from 2009	July Sales Rate (millions)	Months-of-Supply
Off 10%	4.63	10.1
Off 15%	4.37	10.7
Off 20%	4.11	11.4

The peak for months-of-supply was 11.2 months in 2008. And house prices? The Case-Shiller composite 20 index fell 17.2% in 2008.

We are much closer to the price bottom now than in 2008, and I don't expect that severe of a price decline. But I do expect house prices to fall in the 2nd half of 2010 and into 2011 - probably another 5% to 10% for the major house price indexes (Case-Shiller and CoreLogic).

Of course inventory could decline or sales increase a little ... and maybe months-of-supply will only be close to double digits.