Just looking at the statistics page on LJ. From the graph there, it appears that the average age on LJ is somewhere around 16 or 17. The numbers are such that the few people who say they were born in 2000 or 1900 would not modify the numbers much.
Hmmm....I'll never tell.
I just saw a funny cartoon that made me think of several of my LJ friends. In the first frame you see a big fellow standing on his roof with snow all around. He says, "I'm sick of all this snow and cold weather!" In the next frame, you see him jumping of the roof as he says, "I'm going to end it all!". In the last frame you see his shape in the snow by his house and evidently, the snow is pretty deep because the caption is "sigh."
Just upgraded my laptop to the latest LJ client version. The LJ programmers sure do good work!