Here is a link to CBI Team Roster Turnover Insights
Note, just to provide context all information is based on spring rosters (point in time)
Players that are were never on their previous schools spring roster but are list on the new schools roster may or may not be accounted for.
This is most notable with fall dropdowns to jucos, as for the player never officially made the varsity team.
Note, JUCOs are notorious in not documenting the player's previous school, we've tried to fill in this blanks were possible.
Data from PG, PBR Fieldlevel, NCSA on commits would probably fill some of the HS Fall semester transfer holes, but the disclaimer, for example PG is that commit data is not 100%
Outgoing moves are based on
2021 Season (compared against 2020, all divisions reconciled)
2020 Season (compared against 2019, D1 90% reconciled, other division ~ 75%)
2019 Season (compared against 2018, probably 60%)
So you can use the tool to get a baseline number by year and then add a percentage above for the fall transfers
Note, we uploaded the 2021 Fall Roster (as 2022), so you can get a baseline of potential turnover.
Note, this is raw data, so the numbers are skewed. Secondly, not all schools published the fall rosters.