The fourth-quarter earnings season will get underway later this month, and analysts at Jefferies think that the major U.S. wireless carriers are likely going to report weaker margins than they did in the third quarter of 2012. According to a research note from Jefferies analysts Thomas Seitz , Kunal Madhukar and Ankit Sharma, AT&T Mobility (NYSE:T) and Verizon Wireless (NYSE:VZ) are likely to report much weaker wireless margins than they did in the third quarter. AT&T reported a 30.6 percent margin in the third quarter and Verizon reported a 43.4 percent margin. The main culprit comes as little surprise: higher subsidy costs, especially for Apple's (NASDAQ:AAPL) iPhone 5. "Supply constraints on the newly released iPhone 5 in 3Q12 abated in 4Q12, which led to record smartphone sales, and consequently, lower margins across the industry," they wrote.