Interesting research. I think we actually are saying the same thing, but I really can't tell.
It is far too long a conversation to get into about how misleading, if not totally inconsequential, looking at winning percentages is when trying to compare quality across a linear progression. That would be like saying that you could take one of Neyland's undefeated and unscored on teams and expect them to win a single game against modern athletes.
What can be used to determine quality of a team is how they recruit (this is still a flawed methodology, but is far superior to looking at raw wins/losses). What is inarguable is how along a progression going back to 2005 (as far as the data takes me) the SEC as a whole has gotten much more talented meaning that the deviation from most talented to least talented has actually been cut in about half.
In 2005, for instance, here are the four year trailing recruiting averages of many of the teams you mentioned.
Alabama: 30.3
South Carolina: 20
Kentucky: 69.5
Vanderbilt: 93.3
Georgia: 7
Florida: 11.8
Tennessee: 11
in 2015, here are the numbers, and the trends.
Alabama: 1.25 (+29)
South Carolina: 17.75 (+2.25)
Kentucky: 35.25 (+34)
Vanderbilt: (+57)
Georgia: 9.5 (-2.5)
Florida: 9.5 (+2.3)
Tennessee: 11.75 (-.75)
What you see are considerable improvements in raw talent over a ten year period for teams like Kentucky, Vanderbilt and Alabama. What you also see are relatively stable recruiting for teams like Georgia, Florida and Tennessee.
What these numbers show is that in 2005, Tennessee should have gone 5-1 against that schedule due to the relative talent advantage (the only real indication of strength of schedule). And, in 2015 Tennessee should have gone 3-3 due to a relative talent disadvantage. In other words, Fulmer won a great deal of games but with a much larger relative talent advantage than Butch enjoys.
When Vanderbilt and Kentucky are recruiting in 2015 to about the level of talent that Alabama was putting on the field in 2005, it is safe to say that the east is actually more difficult now than it was then.
Further, let us look at the actual talent expectations for these teams in 2015. The chart below shows the numbers that I made on signing day in February. The SEC east has 3 teams that in league play performed exactly as talent would predict, and no teams in the east performed outside of one standard deviation from those predictions. What this means is that, as per usual, talent is a great predictor of success. Couple that with looking at trends over time, and I think it is clear that the east is actually more talented and thus more difficult than it was even a decade ago.
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