property with the subject property (assemblage), could obtain economies-of-scale and added value (plottage value). Similar situations sometimes happen in corporate finance. For example, this can occur when a merger or acquisition happens at a price which is higher than the value represented by the price of the underlying stock. The usual explanation for these types of mergers and acquisitions is that "the sum is greater than its parts", since full ownership of a company provides full control of it. This is something that purchasers will sometimes pay a high price for. This situation can happen in real estate purchases too. But the most common reason for value differing from price is that either the buyer or the seller is uninformed as to what a property's market value is but nevertheless agrees on a contract at a certain price which is either too expensive or too cheap. This is unfortunate for one of the two parties. It is the obligation of a real property appraiser to estimate the true market value of a property and not its market price. Frequently, properties are assessed at a value below their market values; this is known as fractional assessment. Fractional assessment can result in properties that are assessed at 10% or less of their given market values. Market value definitions in the United States In the United States, appraisals are for a certain type of value (e.g., foreclosure value, fair market value, distressed sale value, investment value). The most commonly used definition of value is market value. While Uniform Standards of Professional Appraisal Practice (USPAP) does not define Market Value, it provides general guidance for how Market Value should be defined: A type of value, stated as an opinion, that presumes the transfer of a property (i.e., a right of ownership or a bundle of such rights), as of a certain date, under specific conditions set forth in the definition of the term identified by the appraiser as applicable in an appraisal. Thus, the definition of value used in an appraisal or Current Market Analysis (CMA) analysis and report is a set of assumptions about the market in which the subject property may transact. It affects the choice of comparable data for use in the analysis. It can also affect the method used to value the property. For example, tree value can contribute up to 27% of property value. Main approaches to value There