N.H. Rev. Stat. Ann. § 82:15-a

In making its decision under the provisions of this chapter, when it shall appear to the department of revenue administration that the average rate of taxation upon other property throughout the state is, because of the undervaluation of other property, higher than it would be if such other property were appraised at its full and true value, the department shall give due consideration to the same and make such adjustment as will bring the assessment of the tax hereunder into proportion with the general level of assessments throughout the state.