After carrying the popular handset for just five months, Verizon Wireless is already home to one third of iPhone 4 handsets being used in the U.S., according to analytics company Localytics. The Massachusets-based firm notes that the stat is even more impressive when considering AT&T had an eight-month head start with the popular Apple smartphone. Using data traffic from app usage as a gauge, Localytics determined that Verizon Wireless’s iPhone 4 accounted for 20% of iPhone 4 units being used in the U.S. immediately following its launch this past February. Since that time, Verizon’s share of the iPhone 4 market has grown steadily according to the firm’s data, and it now stands at 32.3%. Verizon Wireless’ apparent rapid growth with the iPhone thus far could be stunted later this year if the iPhone launches on all four major U.S. carriers as BGR speculated earlier this week, but for the time being, the device continues to sell very well for the nation’s No. 1 carrier.