2. Devices

Projected 2017 Growth Over 2016: 3.8 percent

Projected 2017 Spending: $654 billion

Projected 2018 Spending: $677 billion (up 3.6 percent)

Gartner points to mobile phone growth in this category, which it says will be driven by increased average selling prices for premium phones in mature markets due to the 10th anniversary of Apple's iPhone and the increased mix of basic phones over utility phones.

On the other hand, though, the tablet market continues to decline, as replacement cycles remain extended, Gartner said in a statement.