Looking back, high school class of 2020 saw much more waitlist movement than usual, in large part due to uncertainty over covid policies and gap years. Class of 2021 was the opposite, back to normal or worse, no movement, with many colleges full or even overenrolled. My take is that test optional messed with yield management.
I haven’t been paying close attention this year, though presumably colleges are tweaking their yield formulas, and this year is another experiment. Hard to predict. I would take a waitlist spot, but assume not getting off.
Fields for waitlist data are included in the Common Data Set at section C2. Look up the school’s CDS and compare several years’ numbers, 2021 vs 2020 vs some average of years prior to that. Most schools, but not all, have posted their CDS 2021-2022, which includes admission data for high school class of 2021.