The ad tech company has been forced to apologise after time users spent watching videos was inflated as a result of only factoring video views of over three seconds. Discounting shorter views, and users who flat out ignored the video in their news feed, meant reported viewing time was heavily skewed.

It’s a huge step back for Facebook which has pioneered the channel to become a leading source of revenue, driven by some 500 million daily viewers and its banks of targeting-ready data. Financial holding company Nomura had estimated Facebook’s ad revenue from video to reach $3.8 billion by 2017.

“We recently discovered an error in the way we calculate one of our video metrics,” Facebook said in a statement.

“This error has been fixed, it did not impact billing, and we have notified our partners both through our product dashboards and via sales and publisher outreach.”

The social network has since introduced a new metric to fix the problem, replacing it with “average watch time”, while arguing that it represents just one of many used to measure the effectiveness of its placements. For large investors with a high interest on the site, however, the financial scale of the error could be hard to underestimate.

Call for verification

According to WSJ, media buying agency Publicis Media – which purchased approximately $77 billion in ads on behalf of hundreds of global clients throughout 2015 – was told its viewing time figures could have been overestimated by “between 60 and 80%”. Publicis has since called the error “unacceptable”.

The stumbling block has caused many in the online ad industry to question whether Facebook’s statistics should be verified by a third party.

“We can’t have ad tech players marking their own homework anymore,” said Theo Theodorou, xAd’s EMEA MD.

“For a true and fair assessment of viewability, engagement and attribution, having third parties objectively qualifying the insights brands are getting is not only preferable, but is a strategic imperative for creating effective marketing strategies.”