To settle the debate you can look at their
methodology section.
Primary care rating is broken down into:
30%: Primary care rate, or how many primary care physicians the school produces.
25%: Peer assessment score, by medical school deans and other high administrative positions.
15%: Residency director score, by residency directors for primary care residencies only.
15%: Student selectivity, by how competitive it is to enter. Broken down into:
..........9.75%: Mean MCAT score of accepted students.
..........4.50%: Mean undergraduate GPA of accepted students.
..........0.75%: Acceptance rate, or how many applications there are per seat available.
15%: Faculty resources, which is basically the ratio of faculty:students.
Thanks to devilishlyblue for catching my error.