In less than two weeks, more than half of all iPhones are now running Apple’s (AAPL) latest operating system. According to the latest numbers from online advertising network Chitika, the growth rate of iOS 6 among iPhone users has reached 60%, compared to 45% on the iPad and 39% on the iPod touch. The firm notes that iPod touch devices are far more likely to encounter fragmentation due to the large number of first and second-generation devices that are unable to be updated past iOS 4. Unlike iPhones, which users tend to refresh every two years, iPods usually have a longer life cycle. The data come from a sample of millions of mobile ad impressions on the Chitika Ad network collected from September 18th to October 1st. Additional images follow below.