Sociologists Mike Hout and Claude Fischer of the University of California at Berkeley, and Duke University's Mark Chaves used data on religious beliefs from the General Social Survey, a biannual poll conducted by NORC, a University of Chicago independent research institute, to find 20 percent of a nationally representative group said they had no religious preference.
The number of Americans professing no religion is more than double the number reported in 22 years earlier, when 92 percent of Americans identified as a member of an organized religion, the survey showed.
Hout, the lead author of the study, said, "This continues a trend of Americans disavowing a specific religious affiliation that has accelerated greatly since 1990."
Survey questions included, "What is your religious preference? Is it Protestant, Catholic, Jewish, some other religion, or no religion?"
Survey results suggest liberals, men, whites, those between the ages of 18 and 24, and residents of both coasts were most likely to claim "no religion."
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