Earlier this week AT&T reported its fourth quarter fiscal results for 2008, in the announcement Apple’s official iPhone carrier in the United States said that it had activated 1.9 million iPhones during the quarter. The numbers are down from 2.4 million activations in AT&Ts third quarter but the activations as a while have played a key role in AT&Ts growth.

AT&Ts CEO Randall Stephenson attributed iPhone sales as reason why AT&T fought the economy to report revenues up 2.4% (to $31.1 billion).

“The success of our iPhone 3G launch has driven wireless growth and helped redefine the wireless data space.”

Fortune offers some analysis of Apple’s deal with AT&T and in particular what has caused such growth for AT&T in 2008.

AT&T has activated 4.3 million iPhone 3Gs since its launch, 1.9 million in Q4 alone — more than double its iPhone activations one year earlier.
The average revenue from Phone users is 60% higher than the typical AT&T customer — thanks to that $30 per month data fee. Their heavy use of Web services helped drive AT&T wireless data use up 51.2% year to year, which as reader Jon in Brentwood, Calif., points out is not necessarily a good thing.
About 40% of the iPhone activations this quarter were new AT&T customers, either buying their first cellphone or switching from another carrier.
The churn rate — the percentage of customers who drop AT&T’s service — among iPhone owners is significantly lower than the rest of the network, sharply reducing marketing costs.