Facebook has been caught miscalculating viewing numbers for those watching ads on the site.
The company admitted it had wrongly measured average viewing times for video ads by removing views of less than three seconds from its calculations, which helped to bump up the stats.
The mistake overstates median viewing times for video adverts by between 60 and 80 per cent, according to a letter sent by ad-buying behemoth Publicis to its clients, which was seen by the Wall Street Journal.
Facebook, which has been calculating viewing times in this way for two years, told the paper:
We recently discovered an error in the way we calculate one of our video metrics. 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. We also renamed the metric to make it clearer what we measure. This metric is one of many our partners use to assess their video campaigns.
Publicis, in its letter to clients, said the news showed the need for independent, third party verification of Facebook’s claimed performance: “Two years of reporting inflated performance numbers is unacceptable.”
Facebook made revenues of $6.4bn (£4.93bn) and a profit of $2bn (£1.54bn) in its most recent quarter, 84 per cent of advertising revenue now comes from mobile devices, and video ads are an important part of this. ®