When developing for mobile devices, what are some strategies to go about determining which mobile devices and OS versions to support? Do some teams set a certain policy in place, like "support devices used by more than 2% of users" or "support OS versions with over 10% of users?" For example, a reoccurring challenge I am running into is the decision whether to support only new OS versions like iOS7 or KitKat, or continue support for older versions. It would be helpful to know how others approach this decision.