Rankings are irrelevant for top 20 but for the rest it matters a lot. Vast majority of population ends up somewhere outside of top 20. They have to chose betwee

Rankings are irrelevant for top 20 but for the rest it matters a lot. Vast majority of population ends up somewhere outside of top 20. They have to chose between A, B and C and rankings plays its part. Reliable ranking is important because it rewards universities with better enrollment (and vice versa).