- Which geographic regions are covered
- Property value weighting (do more expensive homes have a larger impact on the index)
- Are appraisal values included rather than just sales transactions
- Are houses financed with subprime mortgages and/or non-conforming loans (jumbos) included
- Should foreclosed homes sales be included, given that they may not represent a normal transaction
Here's the Wall Street Journal's look at several different home value indices from November.