The definition of market value as noted by the International Association of Assessing Officers (IAAO) is as follows: "Market value is the most probable price expressed in terms of money that a property would bring if exposed for sale in the open market in an arm's length transaction between a willing seller and a willing buyer both of whom are knowledgeable concerning all the uses to which the property is adapted and for which it is capable of being used." An "arm's length transaction" would be a sale between 2 unrelated parties both seeking to maximize their position from the transaction.
To determine fair market value, actual sales are used. The sales considered are those which occurred 12 months prior to the January 1 assessment date and 6 months after the January 1 date, trended back to January 1.
All arms-length sales are considered bearing in mind that all buyers and sellers are not knowledgeable and that the market is imperfect in that regard. For this reason, one individual sale is not used to determine "market value." In reviewing and researching 18 months of sales, the assessor is able to estimate the approximate price a willing buyer might pay for a property on January 1.