I’ve not looked at this section of statcounter before but I think, as usual, it’s to do with having a huge userbase to begin with (rather than sales). As much as Android and Apple has grown, Nokia has had a big head start, which is helping them maintain a lead in this chart.
Looking back at it in line format, you can see the gradual decline (both of Nokia and Apple it seems). Samsung is the only one making significant one directional growth (to be fair, they have been adapting to the market best, seeing what’s popular and going with it).
In the last half of the year, the rate of decline seems to be more shallow, steadying off in December.
Cheers Anders for the tip!