We estimate Apple shipped 17.7 million mobile phones for a record 34 percent share of the United States market in the fourth quarter of 2012. This was up sharply from 12.8 million units shipped and 25 percent share in Q4 2011. Apple has become the number one mobile phone vendor by volume in the United States for the first time ever. Apple’s success has been driven by its popular ecosystem of iPhones and App Store, generous carrier subsidies, and extensive marketing around the new iPhone 5 model. Samsung shipped 16.8 million mobile phones in the United States, for 32 percent share, during Q4 2012. This was a good performance from Samsung, as its market share rose 5 points from 27 percent a year earlier, but it was not enough to hold off a surging Apple. Samsung had been the number one mobile phone vendor in the US since 2008, and it will surely be keen to recapture that title in 2013 by launching improved new models such as the rumored Galaxy S4.