How has the reaction to the variable of GLA been extracted/isolated? In higher end properties we many times are given several high value items to evaluate. For example, waterfront, waterview, large acreage, etc...
No one is arguing that there are not other factors that influence price. Looking at the graph, at the 2,000sf mark, there is a wide range of values; this implies that there are significant factors at work that influence values for 2,000sf (one of them could be market conditions).
Nonetheless, is it reasonable to draw a conclusion that there a relationship between size and value and that, given the data, the subject is outside the data sample. Further, is it reasonable to argue, based on the data, that there is a diminishing return of value based on incremental increases of GLA after a particular point.
At point $X, the typical buyer will not purchase in this neighborhood; the typical buyer will go to another neighborhood where $X is transacted. And, that is the purpose of the analysis, no? To determine how much value the market can support for GLA differences before the market determines the GLA is over-improved and does not pay any more. :new_smile-l:
That is the benefit of the graph (again): to provide a visual display of the relationship of two variables. The value of the appraiser is to take this data and disaggregate it down to the the specific assignment and make adjustments or weightings that are market-supported.
Do appraisers not collect a similar-type data set every time they complete the 1004mc? In the 1004mc example, the data set is typically smaller because the data is homogeneous (similar to the subject).
I've attached a graph I've completed using data for a property I'm appraising in Santa Clara County, CA; I'm not going to use this graph but I have the data for other analyses I'm completing. I've defined a competitive market area, and have run all MLS sales, detached SFRs, on lots of 6k to 20k. I've circled where the data clusters. Outside of this cluster of prices, it would be
an extraordinary event for a home to sell.
This display illustrates (to the reader and to the appraiser) where this market typically prices homes based on GLA. If one were to value a home outside of the cluster, one would (presumably) need a very good reason to do so; and that reason probably isn't additional GLA. Therefore, analyses like this help the reader (and appraiser) understand how the market is functioning in a one-look display.
And, yes, from this, I can extract (based on the market) a point or range, where there is not enough credible evidence that additional GLA will provide a discernible incremental increase in market value. That is the point of over-improvement for GLA where no additional value is awarded in the market.
Lisle, I think you make (or imply) two significant points
(a) the data can be dorked to show something which really isn't, and
(b) one must be careful about reading too much into the data as there may be other variables.
I'm assuming that the appraiser is not trying to BS the reader.
As to the second point, I agree with DMZ
As with any statistics there is a percent chance they are utter hogwash and that is where the more "standard" appraisal approaches to value come into play. Anyone who relies on a single formula or graph without verifying and supporting the opinion with additional sound appraisal practice deserves to get creamed.