The vast majority of Americans identify with a particular religion, practice their faith to some degree and hold strong spiritual beliefs. Although the U.S. Census Bureau does not ask questions about religious affiliation (it's considered a violation of the Constitution), a number of private and academic polling sources do track religious identification. Their counts indicate significant movement across faiths, as people's religious identities shift and our definitions of religious affiliation, particularly among minority faiths, are in flux.
The U.S. remains a predominantly Christian country. According to the Barna Research Group, 40 percent of Americans say they are evangelical Christians, while 39 percent say they are born again. The Barna group also found that about half of Americans say they are ‚Äútheologically conservative,‚Ä? and 21 percent say they are ‚Äúcharismatic or Pentecostal.‚Ä? A recent study by the Glenmary Research Center, Religious Congregations and Membership: 2000, found that the fastest-growing church denominations in America are conservative Christian churches, with the Mormon church, the Christian churches, the Churches of Christ and the Pentecostal Assemblies of God each growing 19 percent since 1990. Losing the most members were Presbyterian churches and the United Church of Christ, which declined by 12 percent and 15 percent, respectively, since 1990.
But the face of religion in America is changing, due to immigration, waning and waxing denominations and increasing diversity. People are identifying less strongly with a particular religion, and fewer identify themselves as Christian. According to the 2001 American Religious Identification Survey, conducted by the Graduate Center of the City University of New York in 1990, 90 percent of the population identified with a particular religion. By 2001, only 81 percent did so. In 1990, 86 percent of the country identified with a Christian religion; 77 percent did so by 2001.