HOW TO TELL SOMEONE'S AGE when all you know is the name.

My son and daughter don't appear on any of the lists, which must make them uncommon (and of that, there is no doubt). My younger brother is older than me (heh), at least in median age; and my mother and father (both now deceased) have median ages of 64 and 62, respectively.

Something not mentioned, but I'd be curious about: is name popularity cyclical? And if so, as I expect, is there a median cycle length?