GSMA publishes global connectivity scores

Global mobile operator trade association the GSMA has published a Mobile Connectivity Index, which rates pretty almost country in the world according to mobile internet adoption.
The interactive online tool ranks each country on a 0-100 scale which is the average of four sub-categories: quality of infrastructure, affordability of services and devices, consumer readiness for the mobile internet and the availability of locally relevant content.
As you would expect developed economies lead the way