Nate Silver at the New York Times College Sports Blog, "The Quad",
The Geography of College Football Fans (and Realignment Chaos).
Silver explains with the aid of U.S. maps and charts where the fan bases are, which teams are most popular in various markets, etc.
Here is an example from his article for the Big Ten, where the fans of Ohio State, Michigan and Penn State rank not only 1, 2, 3 in the Big Ten, but also tops in the nation:
"Let’s review the results on a conference-by-conference basis with an eye toward realignment. Conferences are listed in order of their aggregate number of fans based on their current configurations.
Silver has data for the other major conferences as well: see the data for your conference here: SEC, ACC, Big 12, PAC12, Big East, Independents including Notre Dame, Conference U.S.A., Mountain West, Sun Belt, Mid-American, and Western Athletic.
All of this information makes it easier to understand what Silver calls the "Realignment Chaos".
As Silver concludes:
"The only two conferences that can feel completely secure right now are the Big Ten and the S.E.C..Go to Silver's article here.
They’re the two that have taken the most conservative attitude toward expansion over the past decade or two, waiting for programs of the caliber of Penn State, Nebraska and Texas A&M to become interested before increasing their ranks. They’ve been rewarded with extreme loyalty among their fan bases. In a sport where rooting interests are so highly localized, that goes a long way toward explaining their success."