Zillow does not allow anyone to store Zestimates or to create a public-facing derivative work with a Zestimate. Therefore, ValueSearch could not be implemented by any 3rd party website using Zestimates or the API. Is this a policy that Zillow is looking to change?

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Ha Ha! I know better than to comment on the accuracy of list prices but no, they don’t go into Zestimate calculations (sales do.) We use the listing’s facts – beds, baths, square feet – to update the database of public tax records. Although public records are a pretty good starting point, a listing is the most current, complete and accurate source of these core home facts for many homes.

Manuel –

If you ever need estimates beyond Florida (or mortgage rates and estimates), please consider using Zillow API’s … http://www.zillow.com/howto/api/APIOverview.htm

Thanks for your clarifications on your product. Does Zillow use listing data to give Zestimates? Because these days, listing prices tend to be way off for value purposes.

Thanks for your feedback!

Besides the non-disclosure issue (UT is voluntary disclosure with a surprising amount of sales that are public), I have not had good experiences with the accuracy of public records in UT. Greg Tracy from Blueroof blog once pulled assessor data and compared it to listing info for 10 Salt Lake listings and 9 out of 10 of the public records were significantly off in important facts like total sq.ft. and number of bathrooms. This quality of raw data causes huge challenges for AVMs like Cyberhomes’ that do not consider the listing agents’ data when calculating estimates. This is another reason to ensure that your listings are on Zillow – the Zestimate algorithm uses the listing data to refine its accuracy.

Manuel –

Zillow doesn’t actually use only one algorithm. Given the great variance in the completeness of public records, I don’t think it’s really possible to use only one model. You’re right about frequency – monthly doesn’t hack it for many people. We’re currently refreshing Zestimates up to 3 times a week.

A local approach seems interesting. I will take a look at the site. Too many homeowners are relying on these AVM’ as value for their home that can be taken to the bank, which is not the case. I think the AVM’s are very useful as an indicator of an area, and trends of an area, but I think that zestimates/etc. on individual homes are a disservice to the homeowner. There are too many variables to consider. Remember, appriasers get ALL of there information from Realtors. The very best market value indicator is what a buyer will pay for the home.

Thanks for your imput!