Perhaps the most striking trend in American religion in recent years has been the growing percentage of adults who do not identify with a religious group.
And the vast majority of these religious “nones” (78%) say they were
raised as a member of a particular religion before shedding their
religious identity in adulthood.
http://www.pewresearch.org/fact-tank/2016/08/24/why-americas-nones-left-religion-behind/
http://www.pewresearch.org/fact-tank/2016/08/24/why-americas-nones-left-religion-behind/