While the guidance it provides for the September quarter is critical the past quarter’s numbers are also important. Over the past three years iPhone unit sales have fallen by 19%, 22% and 21%, respectively, from the March to June quarter. At 40.5 million, which is what I am forecasting, iPhone sales would be down just over 20% quarter to quarter and up slightly year over year. I have reviewed 16 sell-side analyst models and their average iPhone unit sales are 40.8 million, down just under 20% quarter to quarter. If iPhone unit sales fall much more than 20% then there will be concerns about how much the iPhone 8 rumors could impact current model sales.

Source: Forbes July 29, 2017 21:56 UTC