Profile picture for kalvaria

Volatility in Zestimates

The following property dropped signifincantly when Zestimates were restated on June 13.  It wasn't a single month drop, but a 100k adjustment going back through time.  Today, the property is back up by about 100k, but as a spike, not an adjustment.  Can someone explain this new volatility in Zestimates?

http://www.zillow.com/homedetails/810-Shepard-Way-Redwood-City-CA-94062/15571662_zpid/#{scid=hdp-site-map-bubble-address}
  • July 02 2011 - Redwood City
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Answers (3)

Profile picture for blue screen exile
Zillow has indicated they are aware of a number of issues of their new algorithm and that they only did the new calculations from 2006 forward.  They indicated that once they work out these known issues, they will be recalculating from 1996 forward.

As for the rapid fluctuations, that is an indication of the random nature of what sells at any given point in time.  These average out if you have a large enough sample base, but not for an individual estimate.  The area index trend charts and upper and lower tier trend charts give a little better idea of the trend changes.  You need to "smooth" the fluctuations to get a clearer idea of the actual market changes.

As for difference between old and new method?  Here is a sample with the two overlaid for a property that I've been watching:



For the full sized chart to read the text better:
http://photos3.zillow.com/is/image/i0/i7/i6144/IS1nvtyn61couxv.jpg
  • July 02 2011
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Profile picture for kalvaria
Hi.  Btw...love your comps site.  Its the most useful one I've seen.

So, does that mean its permanently adjusted or it might be adjusted again?

Thanks!
  • July 02 2011
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Zillow corrects the incorrect estimate (over estimates or under estimates) on some of properties and the subject is one of them.
http://homesand.net/QuickComps.aspx?810+shepard+way&citystatezip=94062?Map=1?AllComps=True
  • July 02 2011
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