Some time ago, Google removed the pie chart showing the distribution of the Android releases from their Distribution dashboard page:
You can find platform version information in Android Studio's Create New Project wizard.
I made a web tool which gets and displays the Android distribution data from the same source as in Android Studio:
https://andreinitescu.github.io/androiddistributiondashboard/
Open an issue if you see a problem or have any questions. Or feel free to reach me out on Twitter: https://twitter.com/nitescua