One in four Americans are religiously unaffilated and unlikely to switch - study

The proportion of Americans who do not identify with any religion has reached 25 percent. Majority of the unaffiliated had a religious background but they are unlikely to return.

According to the study conducted by the Public Religion Research Institute, most of the unaffiliated grew up with a religious identity. Only 9 percent reported being raised in a non-religious household.

About 19 percent of Americans who grew up in religious households have become unaffiliated when they became adults. Only 3 percent of the Americans who grew up in non-religious households admitted to taking part in a religion as adults.

The retention rates among the religiously unaffiliated also saw a dramatic increase. During the 1970s, only 34 percent of Americans who were raised in a non-religious household remained unaffiliated as adults. The number increased to 53 percent by the 1990s. At present, about 66 percent who were raised without any religious link remained unaffiliated as adults.

A majority of Americans who left their religion did so before reaching adulthood. 62 percent reported leaving their religion before turning 18. About 28 percent said they abandoned religion between the ages of 18 and 29. 5 percent became unaffiliated between the ages of 30 and 49. Only 2 percent have left their religion at the age of 50 or older.

The reasons cited for leaving their childhood religion varied. 60 percent of the unaffiliated Americans said that they simply stopped believing in the religion's teachings. 32 percent said that their family was not religious while they were growing up. 29 percent cited the negative religious teachings about homosexuality.

The unaffiliated are divided into three distinct groups. The Rejectionists, who believe that religion is not important in their lives and does more harm than good, make up 58 percent of the unaffiliated. The Apatheists, who say that religion is not important in their lives but is still socially helpful, make up about 22 percent. The Unattached, believers who say that religion is personally important, only make up 18.

The number of Americans who are religiously unaffiliated started to grow in the early 1990s. In 1991, only 6 percent of Americans did not identify with any religion. By the end of the 1990s, the number has risen to 14 percent. The figure has grown to 20 percent by 2012 and has reached 25 percent at the present.

Daniel Cox, PRRI's research director and co-author of the study, wonders whether the religiously unaffiliated will be voting in the upcoming presidential elections.

"For me the big question is 'will this group come out in November and really throw their weight around?'" said Cox. "They could have considerable impact on the political direction of the country but have so far chosen not to do so."

About 26 percent of unaffiliated Americans have admitted that they did not register to vote.