A new report was released today by the Pew Forum on Religion and Public Life. It provides fascinating insights into religious life in America. It turns out that the religious landscape is very dynamic with a high percentage of people changing their religion during their lifetime.
The survey indicated that 28% of American adults have left the faith of their childhood for another one. If you classify different Protestant denominations as different faiths, then the number goes up to 44%. The figure was much higher for Jehovah's Witnesses. The study showed that two thirds of the adults who reported being raised as Jehovah's Witnesses are no longer in that religion. This helps to explain why they spend so much time knocking on doors. They have to make up for their high turnover rate. See this news article for more information.
See also this intriguing new video about Jehovah's Witness statistics.