The American Religious Identification Survey 2008 survey was carried out during February-November 2008 and collected answers from 54,461 respondents who were questioned in English or Spanish.
The American population self-identifies as predominantly Christian but Americans are slowly becoming less Christian.
+ 86% of American adults identified as Christians in 1990 and 76% in 2008.
+ The historic Mainline churches and denominations have experienced the steepest declines while the non- denominational Christian identity has been trending upward particularly since 2001.
+ The challenge to Christianity in the U.S. does not come from other religions but rather from a rejection of all forms of organized religion.
+ 34% of American adults considered themselves "Born Again or Evangelical Christians" in 2008.
+ The U. S. population continues to show signs of becoming less religious, with one out of every five Americans failing to indicate a religious identity in 2008.
* The "Nones" (no stated religious preference, atheist, or agnostic) continue to grow, though at a much slower pace than in the 1990s, from 8.2% in 1990, to 14.1% in 2001, to 15.0% in 2008.
* Asian Americans are substantially more likely to indicate no religious identity than other racial or ethnic groups.
+ One sign of the lack of attachment of Americans to religion is that 27% do not expect a religious funeral at their death.
+ Based on their stated beliefs rather than their religious identification in 2008, 70% of Americans believe in a personal God, roughly 12% of Americans are atheist (no God) or agnostic (unknowable or unsure), and another 12% are deistic (a higher power but no personal God).
America’s religious geography has been transformed since 1990. Religious switching along with Hispanic immigration has significantly changed the religious profile of some states and regions. Between 1990 and 2008, the Catholic population proportion of the New England states fell from 50% to 36% and in New York it fell from 44% to 37%, while it rose in California from 29% to 37% and in Texas from 23% to 32%.
Overall the 1990-2008 ARIS time series shows that changes in religious self-identification in the first decade of the 21st century have been moderate in comparison to the 1990s, which was a period of significant shifts in the religious composition of the United States.