Yeah true. My mistake, but fair point. I'm not exactly sure how to measure that to be honest. Seeing what people used for ten years without switching would be pretty neat.
Just look at the labour market. Even when companies don't switch languages they constantly have employee turnover.
The only problem is that the labour market is a lagging indicator. Perhaps the best approach is to combine statistics about active switchers (like the OP) with labour market statistics.
