The Pew Research Center for the People and the Press found in its tracking poll last year that 19 percent described themselves as unaffiliated, USA Today reported. Barry Kosmin, who polled on the subject in the 1990s, found that 6 percent of respondents to his Religious Identification Survey said they were unaffiliated in 1990.
"Young people are resistant to the authority of institutional religion, older people are turned off by the politicization of religion, and people are simply less into theology than ever before," Kosmin told USA Today.
Mark Chaves, a professor of sociology at Duke, said young, highly educated people are more likely to shun traditional religious affiliation while many immigrants are from highly religious countries.
Only 10 percent of U.S. residents say they do not believe in God, but that is up from 1 percent a few decades ago, Chaves said.