It's the data we have but the presentation distorts it. To put it another way, for me to had voted on on the poll you mentioned, which I didn't, I would have had to pick UU to avoid choosing irreligious. I wouldn't exactly call myself not religious.Its the best information I've got. Even if you split up that option, its still a lot of atheists/agnostics/irreligious people. I was under the impression that group might be in the top 3 with Christians and Muslims, so maybe I'd expect that group to have a 20-30% share. Its a little concerning that its nearly 50%.