Readers of appraisal reports actually understand that biggest lie repeatedly told in appraisals is that an adjsutment was deirved from a matched pair.....while not always a lie, it often is a lie....how do I know? I know becuase when I ask an appriaser to actually provide the matched pair, they often cannot do it. Aside from that, true matched pairs with only a single different vairable are pretty rare in the real world.
Well, it actually is a LITTLE bit more sophisticated than that. Let say you have two properties that are actually the same except for GLA, BATHROOM_COUNT, and LOT_SIZE.
If can find two other properties that are the same in all respects except for lot size, then I can get an adjustmnet for lot size to use to eliminate that difference between my two comps. Then if I can find two other properties that are only different in BATHROOM_COUNT, I can get an adjustment to eliminate the difference in BATHROOM_COUNT. Now I have only GLA left - and I can take the difference between my two adusted comp values to get the GLA adjustment.
The problem is, really, even that is usually not possible - at least not in the SF Bay Area. Furthermore, just as problematic, you are making these single adjustments usually on a sample size of 1 - which is not at all reliable with so many other factors at play, many of which are not really measurable.
So, it is BS, it is a fraud; although of course, the appraiser is being asked to come up with the most "probable" value - even if it is still highly unlikely to have any reasonable degree of accuracy. It may be rather useless, but if someone HAS to have a value for a forced transaction, then they are really just asking for the "most probable." As far as the lenders and GSEs are concerned, they just see it, in the end, as a problem to solve as best possible. Still, they
apparently distinguish between pure nonsense, guessing and intelligent guessing.