The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.

NEW YORK (

Trefis

) --

AT&T

(T) - Get Report

recently reported a great second quarter in terms of smartphone sales, which is helping drive data revenue growth for the company.

Data revenues for the quarter were up 23% year over year, while the overall revenue grew only 2.2%. Healthy smartphone sales is an important parameter for AT&T to help it compete against

Verizon

(VZ) - Get Report

and

Sprint

(S) - Get Report

.

Our $38.75 price estimate for AT&T stock

is about 25% above market price.

AT&T sold 5.6 million smartphones (including upgrades and new subscribers) in what was the second best quarter for the company. The smartphone penetration, or the number of smartphone subscribers out of the total postpaid subscriber base, is 50%, a 36% increase from a year ago.

ARPU, or the data revenues per subscriber for smartphones, was 1.8 times compared to other devices. This parameter benefits immensely from increasing smartphone penetration.

AT&T stated that the lower-priced smartphone offerings also drove smartphone growth. In particular, it saw solid demand for its iPhone 3GS priced at $49. This is a smart move that capitalizes off the popularity of iPhones and gives many subscribers a way to enjoy the popular smartphone cheaply while driving additional data revenue for AT&T. The company also notes that newer models like the HTC Inspire and Motorla Atrix are selling well.

See our complete analysis for AT&T stock

here.

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This commentary comes from an independent investor or market observer as part of TheStreet guest contributor program. The views expressed are those of the author and do not necessarily represent the views of TheStreet or its management.