As an American, I'm curious what the typical practice is elsewhere for determining if a stall is occupied. I know the little colored marker on the outside of the door is common, but sadly I don't imagine all of our own population being careful enough to notice it. The doors not going all the way down in the US may serve as a more visible indicator of which stalls are occupied without having to bang on the door and get the awkward "occupied!" shout. Not that it completely prevents that rudeness mind you.