10-20 7.41% (2 friends)
21-25 25.93% (7 friends)
26-30 44.44% (12 friends)
31-35 22.22% (6 friends)
36-40 0% ( friends)
41-50 0% ( friends)
51+ 0% ( friends)
However, that means that only 27 of 56 LJ friends I have list their year of birth.
If you want to check your friends' age, go here:
http://www.livejournal.com/community/lj_nifty/125448.html