The American religious landscape has undergone substantial changes in recent years. However, one of the most consequential shifts in American religion has been the rise of religiously unaffiliated Americans. This trend emerged in the early 1990s. In 1991, only six percent of Americans identified their religious affiliation as “none,” and that number had not moved much since the early 1970s. By the end of the 1990s, 14% of the public claimed no religious affiliation. The rate of religious change accelerated further during the late 2000s and early 2010s, reaching 20% by 2012. Today, one-quarter (25%) of Americans claim no formal religious identity, making this group the single largest “religious group” in the U.S.