I'm dubious about the meaningfulness of broad terms like "Christian", "Muslim", etc., because of their coarse granularity. I'm not religious, but from what I observe, I don't think the "Christian" crowd of Catholics, Protestants, Mormons, and Unitarian Universalists would say they believe the Same Thing. I'm guessing that if you asked a C of E whether they were of the same religion as Jehovah's Witnesses, they'd probably look at you funny. Ditto for Shia and Sunni. Such distinctions have great social relevance everywhere. Consider Latin Americans: Catholic vs Evangelical (and that in itself is already a ludicrous simplification) has massive post-colonial, political, and social ramifications; to lump them all as "Christians" is to throw away so much information. It would also be interesting to see a break-down that included people who culturally identify with a "faith" but who are non-practicing (like so many of my Jewish friends).