It looks like they're using a metro region. If you take a look at their "county crosswalk" [1] data that might give more information about it. For example NYC

It looks like they're using a metro region. If you take a look at their "county crosswalk" [1] data that might give more information about it. For example NYC is "MetroRegionID_Zillow" 394913 that has a corresponding "RegionID" in the price to income dataset. [1] http://files.zillowstatic.com/research/public/CountyCrossWalk_Zillow.csv http://files.zillowstatic.com/research/public/CountyCrossWal...