Mass appraisal
Valuing thousands of properties by model rather than one at a time.
Assessors apply statistical models built from sales to whole neighbourhoods at once, adjusting for size, age, and characteristics held in their records.
It is accurate in aggregate and unreliable for individuals. A model cannot know your foundation is failing, that the record overstates your living area, or that the busy road behind you affects value.
This is precisely where appeals win: not by proving the model is bad, but by showing that this property is one it handled wrongly.
Related
- Assessor — The official who values property for tax purposes.
- Record error — The county's file says your home is something it is not.
- Uniformity — The requirement that similar properties be assessed alike — the strongest appeal ground.
Property tax is state law and the details differ. For what applies where you live, see coverage by state and your appeal deadline.