What's the average age of an American convention attendee? Where I live (Ireland), the convention scene is predominantly teenagers around 16/17. As I get older, I feel more out of place. I'm only 22, so I'm not old at all, but everyone else is so much more energetic and there aren't many people my age left. There are still attendees older than myself, but the number is usually in the single digits.

I watched Crunchyroll's livestream of an American convention (A-Kon maybe?), and it seemed to be a bit more diverse. 

I've wanted to visit a larger convention on a visit sometime in the future, so I was wondering what the age demographic usually is for American conventions such as Anime Expo or Otakon.
I've been reading several articles and blog posts about this and I tweeted at a couple of the larger American conventions and one got back to me.

Otakon said that their main demographic is 18 to 28 year olds.

Anime Midwest is not as big as Otakon, but several places online mention the average age is about 17/18.
- "Anime-Midwest: Dear God, I'm Old" 

Anime Boston seems to be reputed for hosting a young crowd.

A large-scale survey seems to indicate the average age for A-Kon in Dallas  is ~24

There seems to be a problem of fans graduating from anime fandom, so that the average age stays the same and cons sometimes face problems with disappointing turnouts because of the constant promotion drive.

Perhaps the larger cons attract older attendees as they might visit them instead of smaller cons because of more work commitments and etc.