Here are the criteria used by the US News to determine the ranking of the Medical schools.
Peer Assessment Score:
Columbia 4.4
Duke 4.4
Michigan 4.4
Mayo 3.9
NYU 3.8
Residency Director Assessment Score:
Columbia 4.5
Duke 4.4
Michigan 4.4
Mayo 4.1
NYU 4.0
NIH funds granted to medical school and affiliated hospitals
Columbia $492 million
Michigan: $435 million
Duke $393 million
NYU $382 million
Mayo $354 million
NIH research grant funds per faculty member
Mayo: $400,000
NYU: $354,000
Duke: $263,000
Columbia: $235,000
Michigan: $224,000
Faculty to Student ratio:
Mayo: 3.4 : 1
Columbia: 3.2 : 1
Duke: 3.1 : 1
Michigan: 2.7 : 1
NYU 2.0 : 1
Median Undergraduate GPA:
NYU: 3.93
Mayo: 3.90
Columbia: 3.87
Michigan: 3.82
Duke: 3.80
Median MCAT Score:
NYU: 38
Columbia: 36
Duke: 36
Mayo: 34
Michigan: 31
Acceptance rate:
Mayo: 2.1%
Columbia: 3.5%
Duke: 3.6%
NYU: 4.7%
Michigan: 5.6%
Unless the ranking is based entirely on MCAT scores and GPA, I have no idea how NYU is ranked 12 spots higher than Michigan.