Press Releases

Zillow.comĀ® Substantially Expands Database of Homes

Real estate site now has data on nearly 90% of all U.S. homes and ZestimateĀ® values on 74%; Improved algorithm, user input boost Zestimate accuracy by 12%

Jan 10, 2008

SEATTLE, Jan. 10 /PRNewswire/ -- Real estate Web site today announced a major expansion and upgrade to its database of nearly all homes in the country -- increasing data coverage from 70 million to 80 million U.S. homes in 48 states, or 88 percent of all homes in the country(1). Zestimate values are now available on three out of four U.S. homes, or 67 million, up 68 percent from when Zillow launched in 2006. New areas with Zestimates include the states of Alabama, Arkansas, Delaware, Iowa, Idaho, Indiana, Kansas, Kentucky, Louisiana, West Virginia and New Hampshire.


Zillow today also announced it has dramatically expanded and improved its Zestimate algorithm, incorporating 20 times the number of statistical models than before that factor in more local and home-type variables and now integrate homeowner-edited home facts -- such as the number of bedrooms, bathrooms or square footage. More than one million homes have been claimed and updated by their owners to date, contributing to improved Zestimate accuracy on many of these homes. Incorporating these changes along with continued algorithm upgrades have resulted in a 12 percent improvement in Zestimate accuracy(2) nationwide. Many larger metropolitan markets, such as the greater San Francisco, Miami, Los Angeles and Atlanta areas, have some of the most significant accuracy gains at 18 percent, 21 percent, 22 percent and 28 percent respectively.

"We've come a long way since Zillow's launch nearly two years ago, adding more data on more homes along with numerous new products and features. The hard work of our team has been heavily supported by an incredible amount of participation from the Zillow community of homeowners, buyers, sellers and real estate agents," said Lloyd Frink, Zillow co-founder and president. "Each day, more than 25,000 community contributions are made to -- things like homeowner updates, photos, or Home Q&A. This type of active participation means a more accurate and transparent real estate community, which benefits everyone."

Zillow Vice President of Data and Analytics Dr. Stan Humphries provided perspective on the magnitude of Zillow's statistical processing effort, "To calculate Zestimates on nearly all homes in America, we process more than a decade of market data to generate over 13 billion historical Zestimates using 67 million statistical models. Our enhanced algorithm along with greater computing resources enable us to process this data at a more granular level than before, resulting in better accuracy."

Unlike most real estate sites, Zillow provides data, information and community features around all homes, not just those on the market today. In fact, 40 percent of all U.S. homes have been searched on Zillow(3) since the site launched in "beta" form in February 2006. With this latest release and round of improvements, Zillow now comes out of its "beta" phase.

More specific details about Zillow's coverage and accuracy down to the county level can be found in its updated data coverage and accuracy pages that now show how often a Zestimate comes within 5 percent, 10 percent and 20 percent of the final sale price, which nationwide is 32 percent, 54 percent and 77 percent respectively. These pages will now be updated every three months, arming consumers and real estate professionals with the most frequent and detailed information possible, supporting the company's commitment to information transparency.

The updated data and accuracy pages may be accessed through a link at the bottom of any page. For more information and commentary from the Zillow team, or to ask a question about the new features, visit the Zillow Blog at

About® is an online real estate community where homeowners, buyers, sellers, and real estate agents and professionals find and share vital information about homes, for free. Launched in early 2006 with Zestimate® values and data on millions of U.S. homes, Zillow has since opened the site to community input, data and dialogue, including "Home Q&A." Zillow's goal is to help people become smarter about real estate -- what homes are worth, what's for sale, and what local experts have to say about real estate and individual homes. One of the most-visited real estate Web sites, Zillow was the only Internet company named by Advertising Age magazine to its 2006 "Marketing 50" list of the most powerful consumer brands. Zillow is headquartered in Seattle and has raised $87 million in funding., Zillow and Zestimate are registered trademarks of Zillow, Inc.

  (1) According to the U.S. Census Bureau's 2005 American Housing Survey,
      there are 91 million single family homes, condos and co-ops in the
  (2) Zestimate accuracy is computed by comparing the final sales price to
      the Zestimate on or before the sale date.
  (3) 37 million American homes have been looked up on Zillow, meaning
      someone visited the property's individual Home Details Page.

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