[skissane]

Some ultra-conservative groups have >80%, even >90% youth retention – such as Older Order Amish and ultra-Orthodox Jews. Jehovah's Witnesses youth retention is a lot lower – I've heard claims it is less than 50%, that on average more leave than say.

Plausibly, being much closer to mainstream culture makes it much easier for people brought up JW to leave, whereas people raised in communities where English isn't even their first language, find that much harder.