While Gregg Swann was busy stirring the pot again (another post sure to bring wrath and retribution raining down on him) and the good folks at Sellsius were busy Carpal Tunnel-ing themselves (don’t these guys sleep?) and Patrick Kitano was explaining my friend Chris Iverson’s real estate “money back guarantee” (heck, if I weren’t an agent myself and I didn’t work for a competing broker, I might just take him up on it!), I was busy trying to answer a question I posed two days ago: how accurate is the data on which Zillow bases their controversial Zestimate?First, a big, big, big, HUGE up-front disclaimer, in keeping with many recent discussions: An automated valuation mechanism (AVM) a la Zillow is not and never will be a substitute for an appraisal done by a professional. It is an estimate, and an estimate only. Improving the accuracy of the data on which the Zestimate is based will not change that fact. ‘Nuff said.Based on my initial highly unscientific look at 10 randomly chosen properties in Menlo Park and comparing the data about those homes as presented in our local MLS vs. county records vs. Zillow, the county gets an accuracy score of 87%, and Zillow gets 84%.I intend to add a number of additional cities to the mix and see what patterns emerge. In the meantime, here are the results… (if you’re a numbers jock and interested in my scoring methodology, scroll down below the chart.)