The Confusing and Fuzzy Math of Internet Home Values, WSJ

Zillow, Trulia and other websites post estimates of home values. But these popular sites can be -- by their own admission -- wildly inaccurate. And for figures that can carry such weight, critics say, the estimates can be far rougher than most people realize. Valuations that are 20% or even 50% higher or lower than a property's eventual sale price are not uncommon, as the sites themselves acknowledge. The estimates frequently change, too—sometimes by hundreds of thousands of dollars—as sites plug new data into their algorithms...All of the competitors make it clear their numbers are guesstimates, not gospel. "A Trulia estimate is just that—an estimate," says a disclaimer on that site's new home-value tool. Zillow goes a step further, publishing precise numbers about how imprecise its estimates can be. And every major site urges home-price hunters to consult appraisers or real-estate agents to refine their results. But despite the disclaimers, homeowners and real-estate agents say, many Web surfers put enough faith in the estimates to sway the way they shop and sell.
By Alyssa Abkowitz, November 13, 2011 WSJ

Link to article

Image credit: WSJ