The number of these Americans has grown by 25% just in the past five years, according to a survey released Tuesday by the Pew Forum on Religion and Public Life.

The survey found that the ranks of the unaffiliated are growing even faster among younger Americans.

Thirty-three million Americans now have no religious affiliation, with 13 million in that group identifying as either atheist or agnostic, according to the new survey.

Pew found that those who are religiously unaffiliated are strikingly less religious than the public at large. They attend church infrequently, if at all, are largely not seeking out religion and say that the lack of it in their lives is of little importance.

And yet Pew found that 68% of the religiously unaffiliated say they believe in God, while 37% describe themselves as “spiritual” but not “religious.” One in five said that they even pray every day.

John Green, a senior research adviser at Pew, breaks the religiously unaffiliated into three groups. First, he says, are those who were raised totally outside organized religion.