A method and machine-readable media are provided for estimating property values. An exemplary method includes obtaining a first estimate of a property from a first property valuation database, the first estimate exhibiting price tier effect bias. The method further includes deriving a price tier effect adjustment factor based on a price tier associated with the property and purchase transaction data. The method further includes adjusting the first estimate to reduce the price tier effect bias using price tier effect adjustment factor, thereby providing a second estimate having reduced price tier effect bias.