Tax officials rely upon sale price of real property to estimate the property's market value. Assessment-ratio studies, which compare the assessed value to market value of property, are a major use of sales data in the tax assessment system. In many States, however, limited verification of sales information collected for ratio studies may compromise the accuracy of data and results of studies conducted. The questionable quality of sales data found in the tax assessment system, plus concerns regarding the adequacy of sales prices of transferred properties to estimate market value of all other properties, most likely restrict uses of these data in research analyses that require a high level of statistical confidence
