From a comScore Blog Post by Andrew Lipsman:
May turned out to be a banner month for mobile as it delivered on some huge milestones which underscored just how impressive the medium’s ascendance has been in the past few years. Mobile platforms – smartphones and tablets – combined to account for 60% of total digital media time spent, up from 50% a year ago. And perhaps more impressively, mobile apps accounted for more than half of all digital media time spent in May, coming in at 51%.
Source: comScore