MOUNTAIN VIEW, CA: More than half of digital ads served to consumers are never actually seen, according to new data from Google.

In a study which set out to understand the factors that affect ad viewability, the internet giant examined its own display advertising platforms, creating a data set with over one week of data from impressions on DoubleClick for Publishers, DoubleClick Ad Exchange and the Google Display Network.

It found that 56.1% of ads had not been seen, compared to an average publisher viewability rate of 50.2%. It concluded that a small number of publishers were serving most of the non-viewable impressions.

According to the Media Rating Council and IAB standards, a viewable impression occurs when 50% of an ad's pixels are on screen for one second.

Among Google's less remarkable findings were that page position matters – specifically, the most viewable position is right above the fold, not at the top of the page – and so does ad size, with the most viewable being vertical units.

But the report also added that above-the-fold positions were not always viewable while below the fold often was. Median viewability for above-the-fold ad units stood at 68% while the comparable figure for below-the-fold units was 40%.

And viewability varied significantly depending on the particular industry. The highest viewability rates were found at "sites associated with more captive engagement". By which Google meant, for example, reference sites or online communities.

By using viewabliity data, the report suggested advertisers could identify both high- and low-value inventory and then shift budgets and targets accordingly in order to maximise reach and ROI.

The importance of viewability was highlighted earlier this year by Aaron Fetters, director of the Insights and Analytics Solutions Center at the Kellogg Co. He told a conference how he had set out to determine the value of viewability by the simple expedient of linking it to sales, with every campaign that was at least 50% in view as the base line.

For ads that were 55% viewed, there was an immediate 18% pop in effectiveness. When the viewability moved up to 65%, effectiveness registered a 41% lift. And when at least 70% of the digital ad was visible, "We had a 68% improvement in the ability of that campaign to move boxes of cereal off the shelf." 

Data sourced from Google; additional content by Warc staff