Facebook announced recently that they only count viewed impressions rather than served impressions. When an ad is served, it just means a request to display the ad was made. Therefore, the ad may have been seen or it may have shown up on the bottom of a page and never looked at. Per Facebook, they have been counting only viewed impressions for the last eight months, and all ad types as well as mobile and desktop ads are tracked this way.
While this is a commendable thing, what they’re saying is accurate only with a given value for “viewed” and “only.” Facebook itself admits that it does not follow the Media Rating Council’s definition of viewable, which is that at least 50% of an ad was on screen for a full second. According to the Wall Street Journal, Facebook counts an ad as viewable if any of it shows up on a screen for any amount of time.
The other issue is that Facebook says it “only” counts viewable impressions. The problem with this is that Facebook is currently unable to determine viewability for a significant portion of mobile ads it serves, and it can’t track it at all for ads served by Atlas. Brad Smallwood, Facebook’s VP of marketing science, has admitted that:
With Atlas we want to push to make sure an ad is viewable before it gets counted, but the technology isn’t there yet to make sure it’s happening
Again, moving towards viewable impressions and away from served impressions is something that needs to happen, and Google has stated that they sell viewed ads not served ads. However, Facebook is trying is trying to create a fairly inaccurate impression of the way they count and charge for ad impressions.
Image Credit: Robert Scoble