http://www.cnn.com/2008/LIVING/wayoflife/02/25/religion.survey.ap/index.html
"The group with the worst retention is one of the fastest growing -- Jehovah's Witnesses. Only 37 percent of those raised in the sect known for door-to-door proselytizing said they remain members."
http://news.yahoo.com/s/time/20080225/us_time/americasunfaithfulfaithful
"An even more extreme example of what might be called "masked churn" is the relatively tiny Jehovah's Witnesses, with a turnover rate of about two-thirds. That means that two-thirds of the people who told Pew they were raised Jehovah's Witnesses no longer are - yet the group attracts roughly the same number of converts. Notes Lugo, "No wonder they have to keep on knocking on doors."