July Android distribution numbers reveal Oreo grows above 10% market share10
If we are to group together Android 8.0 and 8.1, we get a 12.1% market share for Oreo, which is around the same as Nougat one year ago. Speaking of Nougat, Android 7.0/7.1 is still the most used version of the OS to date with more than 30% market share.
At the opposite pole, Gingerbread, Ice Cream Sandwich, and Jelly Bean are the least used versions of Android at the moment, and will pretty soon make it out of the distribution numbers statistic Google releases every month.
That being said, you can find details about how Android OS versions are spread among users in the image attached to the article. It's also worth mentioning that Android Oreo's market share will continue to grow in the coming months, despite the fact that Google is expected to release Android P in August.