[Mailman-Users] number of subscribers

something like:

list_lists -b | while read L; do echo "List is ${L}"; list_members ${L} | wc -l ; done

perhaps?

If you're after something more complicated, that handles archives and
bits,

http://hendricks.amyl.org.uk/~adam/tmp/list-stats

may be of interest

(one day I'll get around to fixing up my repo's browsey thing)

If you want the total number of unique addresses in all your lists, you
can get that with

bin/find_member . | grep "found in:" | wc -l

If you want the sum over all lists of the number of members in each
list, you can do

(for l in `bin/list_lists --bare`; do bin/list_members $l; done)| wc -l