American Religious Identification Survey
The percentage of Christians in America, which declined in the 1990s from 86.2 percent to 76.7 percent, has now edged down to 76 percent. Ninety percent of the decline comes from the non-Catholic segment of the Christian population, largely from the mainline denominations, including Methodists, Lutherans, Presbyterians, Episcopalians/Anglicans, and the United Church of Christ. These groups, whose proportion of the American population shrank from 18.7 percent in 1990 to 17.2 percent in 2001, all experienced sharp numerical declines this decade and now constitute just 12.9 percent.
Baptists, who constitute the largest non-Catholic Christian tradition, have increased their numbers by two million since 2001, but continue to decline as a proportion of the population.
Mormons have increased in numbers enough to hold their own proportionally, at 1.4 percent of the population.
The Muslim proportion of the population continues to grow, from .3 percent in 1990 to .5 percent in 2001 to .6 percent in 2008.
The number of adherents of Eastern Religions, which more than doubled in the 1990s, has declined slightly, from just over two million to just under. Asian Americans are substantially more likely to indicate no religious identity than other racial or ethnic groups.
Those who identify religiously as Jews continue to decline numerically, from 3.1 million in 1990 to 2.8 million in 2001 to 2.7 million in 2008–1.2 percent of the population. Defined to include those who identify as Jews by ethnicity alone, the American Jewish population has remained stable over the past two decades.
Only 1.6 percent of Americans call themselves atheist or agnostic. But based on stated beliefs, 12 percent are atheist (no God) or agnostic (unsure), while 12 percent more are deistic (believe in a higher power but not a personal God). The number of outright atheists has nearly doubled since 2001, from 900 thousand to 1.6 million. Twenty-seven percent of Americans do not expect a religious funeral at their death.
Adherents of New Religious movements, including Wiccans and self-described pagans, have grown faster this decade than in the 1990s.
American Nones: The Profile of the No Religion Population:The 34 million American adults who don’t identify with any particular religious group reflect the general population in terms of marital status, educational attainment, racial and ethnic makeup, and income.