Something like 11-20%, and I'd also say that's true for a lot of people who have said "21-40%" in this topic - though I guess I'm not them so my judgement might be off.
Incidentally, your topic touches on of the two things I consider to be an actual problem on this forum - it's anonymity. There's a lot of interesting people making interesting points around here, but I've got a feeling that 9 out of 10 posts are simply ignored. And good actual discussions don't happen as much as they could. It's specifically visible in threads regarding to music - people just post their favourite/most awesome/whatever songs and ignore every other post in the topic, unless somebody happened to have posted a song they were planning to put up in the first place. Nobody seems to even take the time to listen to eachother's songs or turn the thread into an actual discussion instead of just a random list with songs. I guess this isn't per definition bad, and I realize I contribute to this phenomenom just as well, but it can be kind of... 'depressing' if you make a good point or contribution to a thread and are completely annoyed.