"Trending" is the annual adjustment process that is part of Indiana's move to a market-based assessment system that began in 2002. The idea behind "trending" is to use real property sales data each year to determine if the value of properties in an area should change to match the market value found in the sales of recent properties, thereby making assessments more accurate and more evenly distributing the property tax burden to all taxpayers. Under this system, the assessed value should reflect the amount a willing buyer would pay for the property at the time of assessment.
Annual adjustments are calculated by comparing the prior year assessment with current sales data from a neighborhood. The difference, positive or negative, will be used to create a factor that assessing officials will apply to the property's assessed value to bring it to current market value. When a property owner receives a notice of new assessment, the best way to determine if it is accurate is to ask if the property could have sold for roughly that amount.
For more information, please see http://www.in.gov/dlgf/2338.htm, or call 317.232.3777.