Excell Spreadsheed to calc GLA adjustment

[incognito]

Last year someone posted a pretty cool GLA calculation Excell Spreadsheet, using multiple regression analysis to calculate $/GLA adjustment factors. The name was "automatic Calc & display GLA.xlsx. I have the file, but would like to re-read the thinking behind it, but cannot find the thread which this discussion was in. Does anyone remember who wrote it, or where the thread is? My file date was January 19, 2011, so it may have been around then. I tried a search with no luck... More and more states are looking for sound support for GLA adjustments, and I am thinking of using this to support my market derived factors. Thanks!

 

[incognito]

Well, I searched for hours, then found it just after I asked.

http://appraisersforum.com/showthread.php?t=180913

It is a good read for anyone who wants a good discussion on GLA adjustment factors...

 

[Terrel L. Shields]

Sensitivity Analysis - Mark Ratterman suggests its use as a supportable method of determining a GLA adjustment.

I personally use a similar one for both age and GLA as appropriate. I adjust the sales price by subtracting the land value and making adjustments for any outbuilding or other significant feature difference (garages,etc.)

 

[rbrienza]

incognito, I did not see the excel spreadsheet in the post .. can you post it here.

Thank you

Ray

 

[Meandering]

It's here

http://appraisersforum.com/showthread.php?t=175056&page=5

Metamorphic did it.

 

[incognito]

I have tried, but I am unable to upload an .xls file here. It does not appear to be an approved file type. PM me and I will send it to you. Sorry...

 

[DCSVAL]

just in case

Will this work again?

 

[Terrel L. Shields]

Don't quite understand your question....

.xls files can be read by any version of Excel... xlsx files can be read by newer versions...maybe there is an update for older versions. I have 2003, 2007, and 2010 versions of Word & Excel...so I save a file I have that is similar in 97-2003 formats

 

[DCSVAL]

Thank you for the formula. I keep it on my desktop. And I frequently referred to it when writing my reports. I am curious, sometimes the smallest amount difference is less than zero wish just seems odd. What causes this to happen? I have read through the forum and most of the responses. I understand about iadjusting for condition and various other aspects which might affect the GLA. I would appreciate any thoughts you had on this. Again thank you.

 

[Terrel L. Shields]

Sensitivity analysis is a "what if" analysis. Mathematically, a zero or negative may be telling you that the correlation is not good between the SF and the contributory value you have estimated. This could reflect a distortion in the contribution that relates to incorrect land value, incorrect allocation to outbuildings, etc.

It also may be telling you that there isn't enough difference to justify an adjustment...and if your subject is not bracketed by the sales SF ... this is what can happen. Extreme uniformity will give you a broad range of adjustments...out of range pushes you to negatives... Try a different comp or more comps and the number can change.

Note below, the only thing that changed was the SF of the subject - I really don't have enough math skills to have a better explanation.