Zestimate
Zillow determines an estimate ("Zestimate") for a house based on a range of publicly available information, including sales of comparable houses in a neighborhood. Zestimate does not take into consideration home-specific factors like recent remodeling, although there is an option to update the information for a particular home. The accuracy of the Zestimate varies by location depending on how much information is publicly available, but Zillow allows users to check the accuracy of Zestimates in their own region against actual sales. In many U.S. states, information on the transfer prices of real estate is readily available and accessible by the general public and is not exclusively held in realtors' databases.
In March 2011, Zillow released Rent Zestimates, which provide estimated rent prices for 90 million homes on both the Zillow website and all of its mobile apps.
On June 14, 2011 Zillow changed its algorithm used to calculate Zestimates. In addition to changing the current Zestimate for millions of homes throughout the country, Zillow changed historical Zestimate value information dating back to 2006. This resulted in drastic changes in both past and present Zestimate values for millions of homeowners.
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