In 1971, only 5 percent of Americans claimed no religious affiliation. In fact, until 1993, the numbers of religiously unaffiliated—sometimes referred to as “nones”—never reached more than 8 percent of the population. But something has changed to cause a rapid increase in the abandonment of religion. Today, one-quarter (25 percent) of Americans claim no formal religious identity, making them, according to PRRI, the single largest “religious group” in the United States. Read the entire study here.