A breakout from Smaato of ad spending by category for the second half of 2018 shows that 72% of all spending came from two categories: retail and media. All other categories combined to deliver the final 28% of dollars.
The big story was the 40% growth in retail spending in the second half of the year compared to the frist half. Total retail went from 35% to 49% fueled by online marketplaces Amazon and Walmart, which together accounted for 28% of all ad spending. A lot of that second half spending in retail was likely related to the holidays. Source: MarketingLand