While assessors have a tough job and buyers will tend to look at current assessment as a possible starting point for negotiation, I would observe that data from 2006 is obsolete, to say the least.
The NH Dept. of Revenue Administration monitors the assessment data of all cities and towns and will each year publishes a statewide analysis of the equalization rate in each town. The equalization rate is the ratio between the town-wide assessments and fair market value. So a town that had an equalization rate of 100% would have assessments on a town-wide basis that are equal to what the state believes to be fair market value. The state supposedly requires towns to have assessments within 10% of fair market value ON A TOWN WIDE BASIS.
Within the data of course there could be a much wider variation on a particular property. There are a number of reasons your assessment may not be a good basis for pricing for the market. Craftsmanship, quality of materials, land features (e.g. view, water, etc). Assessors may not be comfortable making big adjustments for things that the market values highly, but are difficult to quantify. The view is a good example. Read my article entitle, What Is That View Worth? at this link http://db.tt/AHsm7hMI
. Privacy is another.
If you provide specifics I will be glad to provide a comprehensive review of pricing metrics for today's market.
Chuck Braxton, REALTOR GRI