It is skewed toward schools with strong graduate programs(weighting of published papers by faculty), larger schools (number of different subject taught), urban schools (# of international students and diversity.
For example with the exception of Dartmouth, Cornell and Williams, every school rated about ND are in large urban centers and are much larger than ND.
And as with most of the these surveys that use the concept of academic rep, there is a bias toward elite old money eastern schools.
Not much ND can do about it.