There isn't a way of telling since JDELIST is comprised of forum users and mailing list users. Theoretically, a JDELISTer can register, login, subscribe to a mailing list and never login again. I suppose that I could compare mailing list subscribers to registered users and then add remaining last logged on users but that sounds a lot like work.
If so, leave it at that. And besides the mailing list users there are many registered users who visit as guests, peruse through the recent threads to find those of interest and leave. I, do that often
Its great to here that our community is having 24000 members. I Congratulate the administrators, the big mans and one and all, who kept this list alive, active, updated and interesting.