It's also worth mentioning that this average is based on tickets sold, not actual butts in the seats. This was increasingly obvious as the season wore on; the announced crowd of 23,572 for the Tulsa game was probably thrice the number of people actually in TDECU Stadium for that game. While the team's mediocre performance through the course of the season probably caused some people to stop going to the games, it's also very likely that a lot of people were so excited by the prospect of a new stadium that they brought extra seats (for example, as part of their season ticket package) that ended up going unused most of the time.
Had Tony Levine remained head coach, the Cougars would probably be looking at a steep decline in season ticket renewals in 2015 which would in turn negatively effect attendance in the coming season. That is no doubt one of the major reasons for his departure (along with the fact that, well, you can't lose to double-digit underdogs like UTSA and Tulane at home and expect to continue to have a job), but it remains to be seen if the new coach will reignite enough enthusiasm among the fanbase to keep season ticket numbers stable.
(Graph updated 1/8/15 to include Houston's bowl game win over Pittsburgh.)