by Calculated Risk on 6/25/2012 06:43:00 PM

On Friday I posted Zillow's forecasts for the April Case-Shiller indexes to be released tomorrow. The year-over-year (YoY) decline in Case-Shiller prices has been getting smaller all year, and the Zillow forecast suggests the YoY decline will be smaller still in April - and be the smallest YoY decline since the expiration of the housing tax credit.

This raises the question: When will the Case-Shiller indexes turn positive year-over-year?

I looked at the recent improvement in prices (comparing the month-to-month changes for the NSA index to last year). At the current pace of improvement, it looks like the YoY change will turn positive in either the August or September reports.

It is important to remember that most of the sales that will be included in the August report have already been signed. The August Case-Shiller report will be a 3 month average of closing prices for June, July and August - and the contracts are usually signed 45 to 60 days before closing. So just about all of the contracts that will close in July have been signed, and probably many of the contracts that will close in August have already been signed.

So any increase in inventory will probably not impact the August Case-Shiller house price report. Note: we haven't seen any increase yet through June, and I don't expect a huge surge in inventory - but others do.

Click on graph for larger image.

Here is a graph of the YoY change in the Case-Shiller Composite 10 and 20 indexes. In March, the indexes were down 2.8% and 2.6%, respectively.

Zillow is forecasting the Composite 10 index will be down 2.4% YoY in April, and the Composite 20 index will be down 1.9%.

Earlier this year, when I argued prices were near the bottom for the Not Seasonally Adjusted (NSA) repeat sales indexes, I thought the year-over-year change would turn positive late this year or early in 2013. Right now it looks like August or September of this year.