Joyce posted good information.
One of the things that appraisers fail to do, and need to do, is ask the question, why are there REO sales for my subject? You need to ask for your own report development, and it helps strengthen the report ( and lessens the chance of it being misleading, if you find out WHY there are a number of REO sales.
A property does not become REO status in a vacuum, and if a number of REO sales are present in a subject building, PUD, or development, why are they there? Were they bought during the high market cycle and the borrowers are underwater and defaulting? Were they property flips that maybe were fraudulant sales the first time around? If it's a condo project, are there building or maint cost issues that are leading to owners defaulting? Is it newer construction that sold too high in initial phase ?
Answer the reasons why the REO's are there, and that could help explain why they are selling for less, and what people are doing with them...are they buying the REO's to live in? To rent out? To fix up and flip?
The answers to these questions help determine the adjustment, if any, for REO status and trend in building. If there are no REO listings, is that a long term trend? Have most of them already been absorbed?
In the past, in declining or stable markets, market evidence was not always there to adjust REO sales up, (but there is evidence in some local areas now, when market conditions are rapidly improving and few or no REO listings are present.).