Connectivity in College Football: 1989 vs. 2009

In 1989, there were 106 Division 1A (now called FBS) teams. A total of 582 games were played between those teams, including 18 bowl games. 52 of the total games (8.9 percent, or about 1 in 11) were played between teams ranked in the Associated Press final top-25.

In 2009, 120 FBS teams played a total of 714 games against one another, including 34 bowl games. Only 38 of the total games (5.3 percent, or about 1 in 20) were played between Associated Press final top-25 teams. (EDIT: Actually, 39 games were played in 2009, 5.5 percent, or about 1 in 19. The infographic doesn't reflect that Clemson and Georgia Tech played twice).

The AP final top-25 was significantly more connected in 1989 than 2009. Only nine ranked teams played at least four games against other ranked teams last season; in 1989, 18 ranked teams did so. Twenty years ago, the AP top-10 either played or shared a common opponent with an average of 17 other ranked teams. In 2009, the AP top-10 either played or shared a common opponent with an average of only 12.6 other ranked teams.

In twenty years, the frequency of games played between top-25 teams has been cut by nearly 40 percent. The primary reason for the decline has been conference expansion. In 1989, 25 teams were independent, including AP final Nos. 1, 2 and 3 and six of the top-25 overall. In 2009, only 3 FBS teams were independent, none of which were ranked. Additionally, there were 94 FBS vs. FCS games played last year, 17 involving AP top-25 teams. Only 50 such games were played in 1989, two by AP top-25 teams.
For more information, see Paul Kislanko who has been doing great work with college football connectivity for several years. See also the AP Poll Archive for historical Associated Press rankings.