Experts say a bit of both. Polling shows that young Americans are considerably less apt to have religious affiliations than earlier generations were at the same age. They attend religious services less often, and fewer of them say religion is important in their lives.
MORE: http://www.washingtonpost.com/local/religion-is-in-trouble-the-word-that-is/2013/07/11/759c6644-e416-11e2-aef3-339619eab080_story.html