T-Mobile US remains the nation's fourth largest carrier, but stands to gain ground from sales of the new iPhone 5S and 5C.
That's because the iPhone 5 became the top-selling smartphone at T-Mobile for the three months ending in August, with 17.1% of the carrier's sales, according to surveys of consumers at Kantar Worldpanel ComTech USA.
T-Mobile's iPhone 5 success and its Uncarrier pricing strategy helped it grow to 13.2% of all U.S. smartphone sales in the three-month period, reversing a trend of smartphone share declines in recent years, Kantar said Monday.
Verizon was the top carrier for the three-month period with 37% of smartphone sales on all platforms, while AT&T had 21.7% and Sprint had 14.6%, Kantar said.
Kantar surveys consumers on a continual basis, conducting more than 240,000 interviews a year in the U.S.
The iPhone first debuted on T-Mobile in mid-April. Of those that purchased an iPhone at T-Mobile in the three months ending in August, 56% switched from another smartphone, including 38.5% from an Android device, Kantar said.
It's no secret that iPhones do well on all the carriers. AT&T saw nearly 61% of its smartphone sales go to iPhones in the three-month period, while Verizon saw nearly 45% go to iOS devices. Figures for Sprint weren't available.
More recent data for activations of the iPhone 5S and 5C at the four carriers since the phones went on sale Sept. 20 show that T-Mobile ranks fourth for activations, with Sprint third, Verizon second and AT&T first, according to analysis by Localytics.
As of Sept. 26, nearly a week after iPhone sales began, AT&T had 1.02% of the U.S. activations, while Verizon had 0.70%, Sprint, 0.12% and T-Mobile, 0.12%.
Also, Localytics found that the iPhone 5S outsold the 5C by 3.4-to-1 just three days after it went on sale. That ratio had decreased to 2.9-to-1 by Sept. 26, with the 5S representing 1.5% and the 5C representing 0.5% of all iPhones activated in the U.S.
T-Mobile offered smartphones at a lower up-front cost under its Uncarrier strategy, with the ability to pay off the phone over two years. Both AT&T and Verizon responded with similar programs in July and August.
"It will be interesting to see if T-Mobile can continue its upward trajectory," said Kantar Strategic Insight Director Dominic Sunnebo.
Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at @matthamblen or subscribe to Matt's RSS feed. His email address is email@example.com.