Answer: 32%
Now I don't have any stats about ACTIVE members, at least not right now. I'm just going by the database.
Consider, though, that I've deleted a lot of users from before 2010 that haven't logged on in a few years. Several banned members from a long time ago were deleted as well.
In other words: like Ignis Ardens, I've cleaned up the user database. If I had never touched the user database, we'd still have 3500+ "members". But since that number really doesn't mean anything, I was OK with removing dead weight. It slows down database operations, which was hurting the site a couple months ago.
The real important stat for a forum is "How many people are usually online?" How many posts are made per day, etc. In other words, how ACTIVE the forum is.