The issue with using the reported Pell Recipients as part of the metric is that it’s based on the 6 year graduating class metric. So the latest Common Data Set repots on the 2017 Cohort.
Then there’s the issue with simply using this metric in the ranking calculation in general (even if it were more current). I think most can agree that from a societal standpoint we want to encourage the ability for lower income students to attend college. But the ranking is generally viewed from an individuals standpoint, not the collective, and unless my student is Pell eligible why would I give two hoots what a specific college’s % Pell recipients is.
I’m sure the colleges are very interested from one year to the next where they are going to rank but I can’t imagine many of them make significant changes to their policies with the goal of moving up that ranking since USNWR (and others) change the calculation pretty frequently and chasing that calculation would be a little schizophrenic.