Interesting summary by Google's AI Overview:
In 2023, 20.5% of FBS rosters were made up of transfer players. In the same year, over 31,000 student-athletes entered the transfer portal, but only about 45% were able to move to new schools.
And from ChatGPT:
The transfer rate in NCAA football has been influenced significantly by the introduction of NIL (Name, Image, and Likeness) rules, with a notable increase in player movement through the transfer portal. Recent reports indicate that the NCAA football transfer rate is around 15%-20%, meaning about one in five players is transferring between programs annually.
With seniors accounting for about 25% of the roster and if a 15-20% transfer rate is "normal", having 25% transfer from a poor team doesn't seem to be out of the ordinary. So a 50% turnover doesn't seem like a very high watermark honestly...
What is sadder is the 45% of transfers that don't find a new dance partner. That should be a word of warning to many...