A government agency and a private information service both have published new housing data in recent days, and they both show lower house prices in St. Louis. They differ sharply, though, on the extent of the decline.

If you look only at data from the Office of Federal Housing Enterprise Oversight, you’ll think the Gateway City has escaped major damage from the housing downturn:  OFHEO’s house price index for St. Louis is down just 0.44 percent in the second quarter, and it’s still up 0.78 percent when compared with the second quarter of last year.

The local picture looks much bleaker in the RPX Monthly Housing Report, published by a firm called Radar Logic. RPX looks at price per square foot, and its measure for St. Louis is down 13.5 percent between June 2007 and June 2008. Over five years, RPX ranks St. Louis among the five worst-performing metro areas, along with Detroit, Cleveland, Sacramento and San Diego.

The truth about the St. Louis housing market probably lies somewhere between OFHEO’s rosy scenario and RPX’s depressing numbers. In a column in June, here’s how I explained the shortcomings of these two measures:

The Office of Federal Housing Enterprise Oversight, source of the positive number, excludes whole categories of home transactions, including those financed with subprime and jumbo mortgages. So it misses most effects of the credit crunch.

Radar Logic’s RPX report, source of the worst negative number, uses a price-per-square-foot calculation that gives a lot of weight to large, expensive homes. It’s probably a good indicator of the markdowns on McMansions, but it may overstate the effect on a modest home’s value.