I think my theory above is a possible answer:
http://www.muscoop.com/index.php?topic=41942.msg630910#msg630910
Other factors:
* People "in front" of you are buying 4 tickets, whereas before they may have been buying only 2. This would be much more prevalent in the cohort where alumni are having kids (or kids are to the age where they need their own seat). May have a small effect if you're in the 30-80 priority point range.
* Alums like me who have been sandbagging priority points. Best seats available at my appt. this year were in the lower corners, about Row E/F/G (depending on 2 or 4), which was slightly better than best available at my appt. last year. But I'm sitting upstairs in non-donation seats, just like I have since graduation because of choice... we've been saying we'll move downstairs next re-seating for the last four years, but we haven't yet. The people who sit around me are in similar situations... we have plenty of priority points to get decent seats downstairs, but we just haven't pulled the trigger for various reasons - mostly because we're "young" (relative to the sweater-vests, despite my wearing a sweater-vest ironically from time to time). But eventually we will, and eventually, so will everyone else, just like the few that did this year.
* The recession is over. I know several people who have downgraded their tickets over the past five years in an effort to save some money, but they still kept building priority points. When my wife and I first had season tix upstairs, we were mostly with other young alums; however, we saw a pretty noticeable influx of gray-hairs into the 400-level end zones right around 2010 or so... people who had been downstairs previously were now sitting upstairs for whatever reason.