CFN has a column up listing the numbers of returning and departing lettermen for each D-1 program.
Here’s the list for the SEC:
SEC
Alabama: Returning Lettermen: 48, Lettermen Lost: 16
Arkansas: Returning Lettermen: 48, Lettermen Lost: 21
Auburn: Returning Lettermen: 51, Lettermen Lost: 23
Florida: Returning Lettermen: 38, Lettermen Lost: 25
Georgia: Returning Lettermen: 45, Lettermen Lost: 24
Kentucky: Returning Lettermen: 60, Lettermen Lost: 20
LSU: Returning Lettermen: 46, Lettermen Lost: 21
Ole Miss: Returning Lettermen: 47, Lettermen Lost: 17
Mississippi State: Returning Lettermen: 43, Lettermen Lost: 22
South Carolina: Returning Lettermen: 54, Lettermen Lost: 12
Tennessee: Returning Lettermen: 45, Lettermen Lost: 25
Vanderbilt: Returning Lettermen: 53, Lettermen Lost: 12
As you can see, Georgia ranks third in lettermen lost, behind two SEC East rivals, Florida and Tennessee.
As an abstract statistic, it’s somewhat hard to judge how meaningful this is. But I would guess that the better the program, the more it matters. I would expect that the better programs have more kids that excel and leave early for the NFL, for example.
Nationally, the two numbers that jump out are USC’s and Notre Dame’s. Southern Cal returns an astonishing 79 lettermen (the majority of whom were highly rated recruits), while Weis is only looking at 30 lettermen coming back in ’07.