No religious group has experienced more explosive growth over the last few decades than the religiously unaffiliated. In 1991, only six percent of Americans identified their religious affiliation as “none,” and that figure had not moved much since the early 1970s. By the end of the 1990s, 14 percent of the public claimed no religious affiliation. The rate of religious change accelerated further during the late 2000s and early 2010s, reaching 20 percent by 2012. Today, one-quarter (25 percent) of Americans claim no formal religious identity, making this group the single largest “religious group” in the U.S.