"I'd say fragmentation hurts retention, which only has secondary effect on adoption." I have no idea how you come to that conclusion. Any conceivable model for

"I'd say fragmentation hurts retention, which only has secondary effect on adoption." I have no idea how you come to that conclusion. Any conceivable model for adoption I can imagine is a differential equation which contains "current adoption" as a term going into the first derivative. If people are leaving a language faster than people are coming in (and I speak in general, not claiming this about any particular language), retention is going to have major effects on adoption and the lack thereof.