Yes.
A value that is assessed for ad valorum tax purposes is a statistical, rather than a discrete, product such as an appraised value. In Massachusetts, the standard for the margin of error for assessed values of improved residential properties is +/- 10% relative to market value.
There also is consideration vis. the valuation date, e.g. the values assessed for FY2003 (ends 06/30/03) in this state are based on the valation date of 01/01/02 and the data used to arrive at assessed values include property sales/rents, etc. that occurred between 01/01/01-to-12/31/01. Other states, counties or cities/town may have different regulations or guidelines, but the systematic lag permits time for data collecton, verification, property inspections, multiple analyses, model adjustments, final value reconciliations and then audit by whatever oversight procedures are legally called for by a jurisdiction. Systematically, assessed values may be generally higher during periods of rapid market price depreciation (and vice-versa) and lag behind market values (or prices paid) since it takes time to reflect the market changes in assessed values. Different jurisdictions have different requirements for the frequency with which their assessed values must be adjusted to market values. In Massachusetts, the minimum requirement is for revaluation every three years with the possibility of adjustment during the interim years.
In the case of an individual property, it also may be possible that the property's description that exists in the assessors' system may not be accurate or, because of the valuation date criterion discused above, may not reflect physical (structural) or market changes that took place between its most recent inventory inspection (or assessment certification) for assessment purposes and the time that the appraiser inspects the property. Therefore the parameters utilized by whatever costing/ depreciation/market adjustment procedures that are statistically applied might not reflect the property's condition/description as of the effective date of an appraisal that is completed subseqently.
Hope this explanation is helpful.
John Mello, MBA, SRA, MAA
MA Cert. General Appraiser and Assessor