a survey found that 16 percent of people who bought the latest iPhones previously owned Android devices
So 16% of iPhone purchases were made by people who previously owned Android phones. (I'm going to assume here that "owned Android devices" doesn't mean you owned a Nexus tablet and now are buying an iPhone.) This statistic is useless, though, unless you also find out how many people buying Android phones previously owned iPhones. If there's an equivalent amount of people getting Android phones to replace their iPhones, then the "16%" isn't really a loss for Android. It's just normal churn. Presenting the 16% figure on its own is misleading as it makes it seem like people are fleeing Android and nobody ever leaves Apple.