The trouble with data is that it can be manipulated to say anything they want. Just look at their figures for GLA and values. How do we know which is the correct value trend?
I did the free trial for Appraisal Loft depreciated cost support for adjustments. You have to go into it and manipulate the quality ratings, condition ratings (without just pulling adjustments out of our assets as they say), but all you are doing is manipulating the data to say what you want it to say. The lot values were pulled out of the air it seems as it valued a similar size lot in a gated community as less than the subject.
We have one county where many of the lot sizes are completely wrong. They will have whole subdivisions with lot sizes smaller than the one story GLA. When you look at the Realist map, you can see the lot size is 2 to 10 times larger than tax records state. You have to do that for the subject and all comparable sales to see real lot sizes. Every time I review an appraisal where some out of town appraiser uses those tax records lot sizes, I know they are not geographically competent for that assignment. Yet, all that data gets fed into the Fannie Data sets.