I have no idea of their popularity, it's a world market. Big Globe.
You must spend money on hiring polsters and surveys to get that data.

yea think of it as dual range..

I have a 2 speed mountain drive geared crank on my Brompton 3 speed, it's slick. 2nd chainring will weigh & cost much less.



[but, with no 2nd chain ring, you can put a bigger low gear on, since the wrap up is just the difference in T count of the rear cluster]






....