Every year the Assessors subject the arms-length sales that occurred in the prior calendar year to a statistical examination based on market area, style of house, age of house, effective area, size of lot, and sale price to see what changes the market has shown. The tables used in the Computer-Assisted Mass Appraisal (CAMA) system are adjusted so that the median assessment of the sales sample is within 10% of 100% of market value and the dispersion of the assessments to sales ratios in the sample are within State guidelines. These new factors are then applied to all properties for the new fiscal year.
Every fifth year the Department of Revenue (DOR) requires each city or town to conduct a revaluation. This is a year-long process during which the DOR examines every phase of the assessing operation before certifying the values. During the four years in between revaluations, the Assessors change the values as sales activity so indicates. These yearly updates are called Interim Year Adjustments.