One of the big financial stories in the tech world this year has been the decline of Apple’s historically high margins that were originally propelled to stratospheric heights by its ever-popular iPhone. But with the high-end smartphone market now over-saturated, Apple has seen demand for its newest iPhone 5 model plateau as budget-minded consumers increasingly choose to buy older models such as the iPhone 4 or iPhone 4S. AllThingsD points us to new research from Consumer Intelligence Research Partners showing that the iPhone 5 accounted for just 52% of all iPhones sold between April and June this year, while the older iPhone 4S accounted for 30% and the iPhone 4 accounted for 18%. It goes without saying that when nearly half the company’s sales come from older, cheaper models then its margins are bound to come under pressure.