That means half were within 14 percent of final sale prices for homes, while those for the other<br />half of homes were off by more than 14 percent — a big discrepancy for the real estate business.<br />The best-known of these tools — the Zestimate, from the online real estate website Zillow — began on the internet 11 years ago<br />and has since amassed a huge audience of homeowners, shoppers and nosy neighbors.<br />Unlike Zillow, Redfin is a real estate brokerage, employing agents to buy and sell homes for clients, which means<br />that its chief executive, Glenn Kelman, regularly hears from Redfin agents who either love its estimating tool or despise it.<br />That means that they shouldn’t be used as more than a conversation point between homeowners, shoppers<br />and their real estate agents when they’re coming up with listing prices and offers for homes.<br />Through refinement of its algorithms and better data about homes, Zillow, now with 110 million<br />homes accessible on the site, has a median error rate of around 5 percent, Mr. Humphries said.<br />Redfin, an internet real estate firm in Seattle, introduced its own home value estimator less than two years ago, commissioning an independent study<br />that showed its figures were more accurate than Zillow’s (Zillow disputes its conclusions).
