As I read the form and complete it, predominant value is the just the, the value of most of the houses in the defined neighborhood. It is not for the greater market area but for the neighborhood which is defined as an area of groupings of inhabitants, buildings or businesses. Most of the predominant values I've seen in reviews are for the market area and are too encompassing.
It has no relationship to subject's value but tells the UW if the subject is "equal to, better than or inferior to" most of the houses in the defined neighborhood.
There are two main ways that I get this number. First is to run a search for all properties that have sold, been listed, expired, withdrawn or are active within my defined sub. From that I judge the type and range of values. The second is to observe the neighborhood houses going in and coming out of the neighborhood. Sometimes I drive in ever increasing circles out from the subject as I leave to see the neighborhood. This is where geographic competence comes in handy.
The ones that are really fun to put down are the rivers where the neighborhood is linear, usually for several miles each way. These values have to come from personal knowledge or the MLS as there is no way you can see the properties without floating down stream in your kayak, an activity not advisable in January or February.
However you do it, most of the time, predominant value is purely a SWAG on the part of the appraiser.
Of course this thread could degenerate if someone asked the question: Is judging the value of the houses in the subject's neighborhood and communicating that "range of value" along with the estimated "predominate" value, considered as an appraisal under USPAP and therefore required to be considered a new assignment with a separate charge and additional fee to the client?
But I won't ask such a question.