How can my assessed value increase (decrease) when I did not do anything to the property in 5 years and I am not selling the property?

The assessed value represents the estimate of market value of the property. The real estate market changes constantly. The assessment for FY 2013 represents the estimate of market value as of January 1, 2012. This estimate of market value is determined by examining sales of properties primarily calendar year 2011. Although there may not have been any physical changes to the property, buyers may be paying more or less for properties than they were in previous years. The assessment changes reflect the changes in the purchase prices of similar homes in the neighborhood. The assessments do not predict market value. The assessments reflect (or report) market value. The real estate market can change dramatically from year to year. Buyers and sellers determine the market value of properties. The assessments reflect what the buyers and sellers are doing as of the assessment date.