Actually, the SF readership is getting older, much older. In fact, this is quite worrisome to both the fans and the publishers of SF. As older readers die off or simply don’t bother to read SF any more for whatever reason, there are not enough younger folks who take up the genre to keep it alive in the future. Sorry, no online sites…I’m apparently not using the correct Google terms. I do know that I’ve read readership statistics in the various prozines and fanzines, though. The age of the average SF reader is going up, way up. There’s a lot of boomers and (SF) golden agers reading SF, not so many teens. Sure, young people will read Harry Potter, but they won’t often check out authors other than J. K. Rowling. What’s more, I believe that the Potter series are shelved among the juveniles/young adults sections in the book stores and libraries, they’re not mixed into the SF/fantasy shelves. I think this is a great pity. I remember realizing that I had really enjoyed a book by a particular author (Andre Norton, as it happens), and then I noticed that she had written other books. (Give me a break, I was in grade school when I realized this.) Then I noticed that all of her books had a peculiar symbol on them, the old “spaceship in an atom” that library SF books used to be marked with. Up until then, I’d been mostly getting my reading material from the Bookmobile. Then I graduated to going to the branch library and exploring the SF section, much to my parents’ disappproval. So I learned that if I liked ONE book by an author, I was likely to enjoy other books by that author, and it was also possible that I’d enjoy other authors in the same genre. I don’t think that kids today get the same opportunities, because most SF/fantasy is written for an adult market, and it’s R-rated, at least. I was careful to screen my daughter’s books and magazines when she was growing up, but someone who wasn’t into SF/fantasy would have regarded this as a chore, instead of a delight, and likely would have banned all SF/fantasy except stuff specifically marketed for younger readers.
Younger people ARE getting some SF exposure through film and video games, but those are more about SF memes, and as I noted earlier in this thread, most all film SF is really, really bad SF. Good SF requires a longer attention span than the average filmgoer or TV watcher is willing to devote to a show.