This isn't something that happens overnight, but each season we'll see tickets struggle to sell more and more, as
@M23 Citizen pointed out, even comparing this season to last season there has been a reduction in demand.
20 years ago my nephew was in school and loads of kids in his school went to watch city each week. Now my lad is in school, and he's pretty much the only one in his class who goes to games.
That may not be a problem tomorrow, or in a few years time, however in the Long Run that could turn out to be a huge issue when older fans start going and there's no younger fans to replace them.