It is a hard problem, but the fact they are touting their Zestimate, and having the values so ridiculously off, gives me no confidence in Zillow. And it hasn't

It is a hard problem, but the fact they are touting their Zestimate, and having the values so ridiculously off, gives me no confidence in Zillow. And it hasn't gotten any better since Zillow first started, which makes me have even less faith in them. If they backtested their data and corrected for it, or had some sort of machine learning algo, I would bet it would get a lot better. To me, it looks like they are using a simple average $/sqft algo and it looks like they go back a year or so to determine this $/sqft without a higher weighting to more recent house prices. If they have Redfin agents bidding in the area, they can pipe in the price their clients bid for certain houses, and use whether or not they got the house as a training data point as well.