One key trend that Apple (NASDAQ: AAPL) investors have taken note of recently is the company’s precipitous rise in research and development spending. As a percentage of revenue, Apple’s R&D expenditures would historically stay within a 2% to 4% range, but in recent years this has climbed to 4% to 6%. That translates into an awful lot of spending in dollar terms when you factor in Apple’s growing top line (2016 notwithstanding).