Jelly Bean was running 59.1% of Android devices in December

As time goes on, we should see KitKat's percentage rise as the number of Android models running on Jelly Bean stabilizes and the use of the Ice Cream Sandwich builds decline. The information covers Android devices that visited the Google Play Store over a 7-day period that ended January 8th.

Jelly Bean was the most used build of Android in December
source: Google