The other day someone sent a message about a list with about 900
subscribers, indicating that it was a somewhat large list.  What
would be considered a small, medium, large list?  Wouldn't the focus
of the group (more popular v more esoteric subject matter) have
an impact on how large a group might be?  Additionally, has a predictable
rate of growth over time been noted in connection with these groups.
Does anyone know of any literature that addresses these issues?
 
Thanks,
Paula