When you see the figures Saige gives above, one might be led to think that the remaining 93% of the population must be religious. However, being religious and being religiously "devout" are two different things.
In a 2000 Gallup survey, two-thirds of Americans claim to be a part of some religious institution. The remaining one-third is divided between the atheist figure (which the Gallup survey places at 5%) and other "non-traditional approaches to organized faith." Going further, six out of 10 Americans say "religion is very important in their lives." Only 36% of the population says they attend religious services every week.
Interestingly, 45% of Americans say they follow "their own views and the views of others" as opposed to a strict following of their religious teachings.
Overwhelmingly though, church attendance is down in America in the last decades. Major denominations report falling membership rates across the board, as rates in fundamentalist, evangelical, and Pentecostal sects rise. Religious dogma is being dropped in favor of "cafeteria style" faith, where "spirituality" overrides institutionalized teachings.
All these statistics should be analyzed with hesitancy, however, say sociologist Stanley Presser and researcher Linda Sinson who place the church attendance figure around 26%.