The distribution of various Android versions can point us to various conclusions, one of them being, the life span of a single version may approximately last between 3 to 4 years.
As you can see, Jelly Bean (4.1, 4.2, 4.3) which was initially released on July 2012 is still one of the most popular versions on the platform to date.
Another conclusion that can be drawn based on the stats gathered recently is that Lollipop, the latest Android version, released over 9 months ago that brought multitude of new features (such as Material design), is still not the most popular version, although it seems heading that way.
It could be that one of the main reasons for the slow adoption of Android’s latest versions (this is not the first time) is its compatibility with older devices among other factors such as manufacturers will to incorporate their own design and apps on top of Android devices they sell.
Beyond that, yet another interesting diagram to note is the Open GL version distribution which is the graphics library that affects the smoothness of the display (by enabling hardware-accelerated rendering).
It is somewhat unfortunate to note that the older Open GL version (2.0) is still being the most widely supported version instead of the newer ones which holds more features.
Nevertheless, granted that most users aren’t running the latest and greatest Android version it is somewhat understandable and perhaps even expected.