By Brad Edwards

(CBS) — The number of Americans who describe themselves as Christians is dropping and these days, when young people are asked what religion they are, the answer that’s becoming more popular is “none,” as in no religion at all. But why?

On the ultimate frisbee fields of Northwestern, CBS 2’s Brad Edwards found the ultimate example of a “none.”

“My father was Jewish, I was raised Catholic,” said Sam Cooler.

Cooler is now a grad student and doesn’t identify.

“I have a scientific viewpoint on many things,” he said.

He’s one of the now more than one third of millennials who are unaffiliated, and science is an oft-cited reason.

Dr. Michael Murphy, a theology instructor at Loyola University, says, “There staggering in lots of ways but they’ve been trending that way.”

In 2007, 78.4 percent of Americans identified as Christians. Now, it is only 70.6 percent, a nearly eight percent drop in eight years, according to a study by Pew Research.

No faith affiliation or “nones” now make up 23 percent of U.S. adults, as the numbers of evangelicals (25.4 percent) Catholics (about 21 percent) and mainline Protestants (14.7 percent) continue to drop

But why the drop?

“I think millennial in particular are wary to contemptuous of big institutions in general,” said Dr. Murphy.

Whether it’s big banks, government, the churches sex abuse cover-up, Murphy says and he adds, “The idea of being a community, which the church are always major in, is different now and it’s really coming to roost in these new findings.”

Dr. Murphy says there’s a cyclical nature to belief, and right now there is an ebb.

Brad Edwards