Friday morning, Verizon reported its third quarter results. As a part of its presentation, the company included how many iPhones it sold during the quarter. With AT&T having reported on Thursday, this gives us the opportunity to see how the market share for U.S. iPhone sales is changing among the two carriers.

Here's the chart showing market share:

iphone att v verizon 2011-q3.png

Verizon actually started pretty strongly in the first quarter. Its performance was even more impressive at that time if you note that it only sold the product for about half as long as AT&T did during the period. The Verizon iPhone was released on February 10th.

The market share was similar the second quarter, but Verizon began to make a bit more progress in the third. Its market share rose a few percentage points to 43%. This doesn't show very strong preference for AT&T among iPhone customers last quarter compared to Verizon. It's also worth noting that AT&T also sold the iPhone 3Gs during this period at a significant discount to the iPhone 4, which provided the company a larger spectrum of potential new iPhone subscribers than Verizon.

As I wrote yesterday, this quarter will be the real test for these companies. For the first time a new version of the device, the 4s, will be released on more than one carrier simultaneously, with Sprint joining the fun. The race is really AT&T's to lose: most customers upgrading from a previous iPhone version will be AT&T customers. To the extent that they don't want to deal with the headache of switching carriers, they'll stay with AT&T.

Most of Verizon and Sprint's iPhone sales will come from its customers upgrading from other mobile phones and new customers. That is, unless AT&T sees an exodus of existing iPhone customers upgrading to the 4s who are frustrated with its network. We'll know in three months!

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