Renorming: why categories shift year to year

•    What it is — IDEA periodically refreshes the comparison numbers (average and spread of scores) a rating is measured against, instead of using a fixed, aging baseline forever.

•    Why it happens — Ratings nationally tend to drift upward and cluster more tightly over time, so the comparison data needs refreshing to stay meaningful.

•    Who it affects — National, discipline, and institution comparison groups can each renorm on their own timeline; discipline and institution groups typically refresh using the most recent five years of data.

•    What it means for you — A category label reflects standing against current peers, so it can shift slightly year to year even with consistent teaching.