comScore has published its latest MobiLens stats on the US mobile market, and they show Apple and Google tightening their grip on smartphone usage there.

The stats, which focus on smartphone usage rather than new device sales, show Android increasing its US smartphone market share from 50.9% in May 2012 to 52.6% in August. In the same period, iPhone grew from 31.9% to 34.3%.

That means between them, Apple and Google account for 86.9% of smartphone ownership in the US. The big loser over the past five years has been RIM, which saw its share fall from 11.4% in May to 8.3% in August, according to comScore. Microsoft’s Windows Mobile/Phone platforms dipped from 4% to 3.6%, meanwhile.

comScore also has data on what people are using their mobile phones for. In August, 53.4% of all US mobile users – smartphones and feature phones included – used downloaded apps. Meanwhile, 52% used their browsers, 38.3% accessed social networking sites or blogs, and 34% played games.