FORTUNE — According to the chart above, drawn from comScore data and posted Friday by Asymco‘s Horace Dediu, sales of Google Android smartphones in the U.S. peaked in December 2011.

Sales of Apple (AAPL) iPhones, by contrast, continue to grow in the U.S. Dediu attributes that to broader distribution (three of the four major U.S. carriers, soon all four), availability of three iPhone models at price points that start at $0, and increasing awareness of the value of the Apple ecosystem.

It remains to be seen whether the rest of the world — where Android is still on a tear and the iPhone is not as widely distributed — follows the pattern set by what was in December 2011 (before China eclipsed it) the world’s largest smartphone market.

For more, see Dediu’s Reasons for iOS outperformance in the US.