Here are some preliminary insights on Player Attrition for the Pac 12.
Total outgoing - not on current roster
Potential Graduation - Previous year's (Seniors or Grad students) not on current roster
MLB Draft signed - Previous year's players that were drafted and signed
Transferred out - Previous year's players that transferred to another school
Unknown Reasons - Don't know why player is not on current roster.
*** Note, currently most players will be listed as unknown, this will change when other schools are published and player data is reconciled.