The structure of an industry is changed over time by firms both entering and exiting it. For example, when Apple introduced its iPod, it had a monopoly in this product space since no other manufacturers sold any devices like it. But over time, competitors being lured by profit potentials, introduced their own products such that the industry structure for mp3 players changed from being a monopoly into one that became more competitive as more similar products began appearing in the mp3 player product space.

Smartphones have largely displaced stand-alone mp3 players. Describe the effects of this on the mp3 player industry focusing more on how this industry has changed. Include some discussion of Apple's response to the changing industries conditions over time to as far as what they are more-recently.