With half of every dollar spent on digital advertising going toward search, it remains the most crucial channel for marketers to get right. It is a maturing category, with demand for paid ads via search engines humming steadily. But when we take a peek under the hood, it becomes apparent that the gears driving this market are shifting furiously as marketers seek to reach users on a growing roster of devices. To assist marketers with this mission, our forecast includes an analysis of the shifts in US search users, volume, and spending across PCs, tablets, and mobile phones as well as spending across 12 industry verticals.