Real estate appraisal, property valuation or land valuation is the process of developing an opinion of value for real property (usually market value). Real estate transactions often require appraisals because they occur infrequently and every property is unique (especially their condition, a key factor in valuation), unlike corporate stocks, which are traded daily and are identical (thus a centralized Walrasian auction like a stock exchange is unrealistic). The location also plays a key role in valuation. However, since property cannot change location, it is often the upgrades or improvements to the home that can change its value. Appraisal reports form the basis for mortgage loans, settling estates and divorces, taxation, and so on. Sometimes an appraisal report is used to establish a sale price for a property. Besides the mandatory educational grade, which can vary from Finance to Construction Technology, most, but not all, countries require appraisers to have the license for the practice. Usually, the real estate appraiser has the opportunity to reach 3 levels of certification: Appraisal Trainee, Licensed Appraiser and Certified Appraiser. The second and third levels of license require no less than 2000 experience hours in 12 months and 2500 experience hours in no less than 24 months respectively. Appraisers are often known as "property valuers" or "land valuers"; in British English they are "valuation surveyors". If the appraiser's opinion is based on market value, then it must also be based on the highest and best use of the real property. In the United States, mortgage valuations of improved residential properties are generally reported on a standardized form like the Uniform Residential Appraisal Report. Appraisals of more commercial properties (e.g., income-producing, raw land) are often reported in narrative format and completed by a Certified General Appraiser. Types of value There are several types and definitions of value sought by a real estate appraisal. Some of the most common are: Market value – The price at which an asset would trade in a competitive Walrasian auction setting. Market value is usually interchangeable with open market value or fair value. International Valuation Standards (IVS) define: Market value – the estimated amount for which an asset or liability should exchange on the valuation date between a willing buyer and a willing seller in an arm's length transaction, after proper marketing and where the parties had each acted knowledgeably, prudently and without compulsion. Value-in-use, or use value – The net