From PBS NEWSHOUR: "Fewer Americans are calling themselves Christians"

The trend is evident across all demographics, but one group in particular stands out, the Millenials:

     The pattern could be seen across all genders, races and education levels. However, one demographic that stood out was an group. As Millennials replace previous generations, they bring with them their low religious affiliation: 34 percent of older Millennials and 36 percent of younger Millennials consider themselves religiously unaffiliated.
     At the same time, Millennials are not the only age group to be losing their religious affiliations. “people in older generations are increasingly disavowing association with organized religion,” the report read. “Nearly a quarter of Generation Xers now say they have no particular religion or describe themselves as atheists or agnostics, up four points in seven years. Baby Boomers also have become slightly but noticeably more likely to identify as religious ‘nones’ in recent years.”