According to Google's latest report on Android versions, Lollipop is nearly at the 30% mark while Marshmallow has yet to score its first percent. While we watch the monthly pie charts with interest, they omit the story of how we got here.
This animated version of Android releases over the years does a much better job of this. It shows how new versions grow eagerly, while old versions are reluctant to leave. Watch out for the blue segment of the 2.3.x branch – that's the long-lived Gingerbread, which took years to fade into oblivion.
There's even an app so that you can watch this on your Android phone if you want to be meta.