Marin Software's Digital Benchmark Report for Q4 2017 shows that:

• Although social clickthrough rates remained relatively flat, social CPMs increased by an average of 44% from 4Q2016, up from $2.03 to $2.94.
• Although mobile CPCs remained lower than desktop CPCs, the average price of a mobile CPC rose 25% in 2017.
• Mobile share of PPC ad spend had risen to 53% by the end of 2017.
• AdWords advertisers using few ads per ad group aren't getting the full benefit of Google's machine learning technology and optimized ad rotation.
• Only 24% of advertisers are using and measuring the results of audience targeting.

Actionable: Get the wonderful technologies available from Google and social-media platforms working for you. Identify, target and measure results for audiences. And create enough AdWords ads for every ad group to enable Google's machine learning to optimize your search term - ad - landing page matching.