There's a simple reason people aren't buying iPhones like they used to (AAPL)

Apple shares fell 4% on Tuesday and were down more than 2% in premarket trading on Thursday amid growing concerns around a slowing iPhone cycle.
At least four of the tech giant's suppliers have cut their own guidance due in part to weakness in the smartphone market. 
The slowdown in the smartphone market is due largely to rising prices and consumers holding onto their models for longer periods of time relative to previous cycles, one bullish analyst said.
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