T-Mobile will be the last of the big four wireless carriers in the United States to offer the iPhone when it launches in the next month. The company’s new “UNcarrier” initiative could make it an appealing choice for consumers looking for a contract-free plan. Horace Dediu of Asymco estimates that T-Mobile could sell about 3.4 million iPhones in 2013, totaling 10% of its subscriber base. The analyst’s sales numbers are based off trends from AT&T (T), Verizon (VZ) and Sprint (S), along with the percentage of total subscribers that each operator has been activating. Dediu notes that the sales patterns are consistent across all carriers and that the longer the iPhone is is available, the higher the activation rate. He estimates that iPhone sales across all four major carriers will reach 53 million in 2013, accounting for 17% of 320 million subscribers, an increase from 14% in 2012.