• by Erik Sass , Staff Writer @eriksass1, October 20, 2015

Facebook scores highest in advertising effectiveness among the leading social media platforms, according to a survey of brand and agency executives from 29 big companies conducted by eMarketer. But there’s still a lot of room for improvement, marketers say, particularly in the area of -- you guessed it -- measurement.

Asked to assess social media with the “A-F” system which haunted our childhoods, marketers gave paid social media overall an average grade of B for its ability to drive return on investment -- respectable, but hardly going to get you a new bike. Leading the pack was Facebook with a B+ for ROI, followed by Twitter with a B- and LinkedIn with a C+.

Three emerging social media platforms rated lower when it came to ROI, with execs giving Pinterest an average grade of B, Instagram an average of C+, and Snapchat an average of C-.

Turning to targeting, overall marketers gave Facebook an A for its advanced targeting capabilities, while Twitter and LinkedIn both got a B. Among the emerging platforms, Instagram got a B, Pinterest got a C+ and Snapchat got a C- when it came to ad targeting.

Across the board, marketers said that their ability to measure the impact of social media advertising on their bottom line had improved, but still wasn’t where it needed to be.

The eMarketer survey polled execs about a number of other categories as well. For example, Twitter earned a “B” in areas including creative, building brand awareness and engagement, and driving actions, while among the emerging platforms Instagram and Snapchat also excelled for creative and building awareness and engagement -- but didn’t do as well in ROI, reflecting their newness.

Asked about video, marketers gave Facebook a B+ as a video platform, the same grade as YouTube, but added that the two platforms serve different purposes in their video strategies. By contrast, Twitter received a B- as a video ad platform.