85-90% stay. But 10-15% leave. That's thousands of people each generation.
When
Before baptism (16-22) — no consequences. You simply didn't become Amish. Family is sad but stays in contact. After baptism — Meidung (shunning). More serious: family turns away.
Why They Leave
Education (want to study further). Career (want to be a doctor, engineer). Freedom (want to drive, travel). Faith (lost it or found another). Love (fell for an 'English' person). Rebellion (fed up with rules). Everyone has their reason.
What Happens Next
Hard. 8th-grade education. No driver's license. No credit history. No résumé. No social network (both senses). Many first years in low-paying jobs. Some support programs exist (Mission to Amish People, etc.).
Return
Some return after years. The world wasn't what they expected. Loneliness, competition, meaninglessness. Community accepts back (through repentance). Full forgiveness. Past forgotten.
Fact
Leaving rate is DECLINING: in the 1950s, 20-25% left. Today 10-15%. Is the world becoming less attractive? Or the community getting better? Probably both.