I wonder how much of that is user aging out of active usage for one reason or another (retirement, switching to a tablet from a desktop, etc) and how much of it

I wonder how much of that is user aging out of active usage for one reason or another (retirement, switching to a tablet from a desktop, etc) and how much of it is people switching (and how much of that switching is to something newer and small (e.g. not Safari, Edge, etc).