Traditionally speaking religion was a term used for the main faiths like Judaism, Islam, Eastern philosophy & Christianity. On the other side of the coin were the non-religious people who reject spiritual entities & tend to hold to a Materialist mind set yet the non-religious are in fact very religious & hold to miracles that actually go against the laws of nature that had to come from somewhere. Both sides of the coin although different at face value hold the same properties & that is faith in something that is unobservable. http://creation.com/five-atheist-miracles.
For some people God is nature & nature really has done the impossible in their eyes even though they can’t prove it & hence all the arguments. So when a census tells you people are not as religious anymore I would say not so, people are just as religious & bound by belief dressed up in unscientific science.Naturalism, Scientism & Materialists have their doctrine & evangelical outreach programs, government funding & assistance & the like & it seems to me a clever deception & a very tangled web is at play on many dimensions.