Market/data approach - A method of appraising or evaluating real property based on the proposition that an informed purchaser would pay no more for a property than the cost to him or her of acquiring an existing property with the same utility. This approach is applicable when an active market provides enough quantities of reliable data that can be verified from authoritative sources. The approach is relatively unreliable in an inactive market or in estimating the value of properties for which no real comparable sales data are available. It also is questionable when sales data cannot be verified with principals to the transaction. Also referred to as the market comparison or direct sales comparison approach.