According to the government, home values edged lower last month.

The Federal Housing Finance Agency's Home Price Index report shows values down by 0.3 percent from the month prior -- the index's first down month since April.

The Home Price Index is based on the value of homes financed via Fannie Mae or Freddie Mac and, in this sense, the FHFA Home Price Index is more of a "national" real estate index than its private-sector cousin, the Case-Shiller Index.

But like the Case-Shiller, the HPI is as notable for what it specifically excludes as for what it includes. Most notably, the Home Price Index doesn't account for homes meeting any of the following descriptions:

1. Is considered new construction
2. Is a multi-unit property
3. Is financed by an entity other than Fannie Mae or Freddie Mac

Given the resurgence of FHA financing this year, this last exclusion is especially glaring.  FHA represents about one-third of all mortgage loans in 2009.

Because of these exceptions, some analysts label the Home Price Index incomplete.  The same could be said of every method of home valuation, however. Case-Shiller only collects data from 20 markets, for example.

In light of these shortcomings, therefore, what's most important is to recognize that both of the "popular" home valuation reports show similar patterns -- home prices have leveled and are showing signs of a rebound.

For a region-by-region breakdown of the Home Price Index, visit the FHFA website.