"More than one-quarter of American adults (28%) have left the faith in which they were raised in favor of another religion - or no religion at all. If change in affiliation from one type of Protestantism to another is included, 44% of adults have either switched religious affiliation, moved from being unaffiliated with any religion to being affiliated with a particular faith, or dropped any connection to a specific religious tradition altogether."
"To illustrate this point, one need only look at the biggest gainer in this religious competition - the unaffiliated group. People moving into the unaffiliated category outnumber those moving out of the unaffiliated group by more than a three-to-one margin. At the same time, however, a substantial number of people (nearly 4% of the overall adult population) say that as children they were unaffiliated with any particular religion but have since come to identify with a religious group. This means that more than half of people who were unaffiliated with any particular religion as a child now say that they are associated with a religious group. In short, the Landscape Survey shows that the unaffiliated population has grown despite having one of the lowest retention rates of all "religious" groups."
*Jehovah's Witnesses have the lowest retention rate of any religious tradition. Only 37% of all those who say they were raised as Jehovah's Witnesses still identify themselves as Jehovah's Witnesses.