The indefatigable Horace Dediu points out on Asymco.com that although Apple's (aapl) iOS and Google's (goog) Android are less than two years old as platforms, together they have captured 50.2% of what he calls "the most competitive market technology market on the planet."
Below: The same data graphed as market share.
<!-- more -->
Also on Fortune.com:
[Follow Philip Elmer-DeWitt on Twitter @philiped]