Around the turn of the century, Apple was spending well more than 5% of its sales on R&D as it tried to recover from its near-death experience in the late 1990s. That investment resulted in a string of hits — the iPod and iTunes and later the iPhone and iPad — that turned its business around and turned Apple into a tech giant.
As Apple's sales soared, its R&D investment didn't keep pace and reached a nadir in its 2012 fiscal year, when the company devoted just 2.1% of its revenue to its research effort. Since then, though, the company has been gradually devoting more and more of its sales to R&D. In its last fiscal year, Apple spent 5.4% of its revenue on research and development — the highest allotment for its R&D effort in 13 years.