Also historically average age of first menses in native
       Japanese women occures much later than women in the 
       USA.  I supect that that average age of first menses in
       women in Japan is dropping (younger average age for 
       first menses.)  as their diet has changed since WWII.  But
       I do not have the facts in front of me.  I believe (if I
       remember correctly) that for some rual Japanese women the
       age of first meneses could be as late as thier early 20s!
       Note this is from memory.

       PS: the "hsc" in my address is for Health Science Campus,
       we tend to sutdy such things.

Um.... being a girl... maybe I should try and give my viewpoint. Girls get
their periods when their bodies reach a "prime weight". A girl's period will
not start before then. Girls who are 9-14 who seem very developed for their
age have reached the "prime weight" and began their period. It is very rare
for girls to have breast development (to a noticible size) if their period
has not started yet. My friends who were like 5'8-5'10 (i.e. tall for their
age) and thin with little breast development usually did not start their
periods until they were 16-18 because they were too thin and hadn't reached
the proper body weight and temperature yet. It was *very* noticible when
they did because they began to 'round out' instead of being tall, thin, and
gangly, even though they generally never got as much breast development as
the girls who had started early in life. Ranma who is *stacked* as a girlm
hypothetically would have started a period young. :)