Facebook has admitted to accidentally reporting incorrect advertising metrics for the past two years. In a statement, the social network said that it “recently discovered an error” in the way it calculated video metrics, and that it had notified advertising publishers. The error meant that measurements of time spent watching ads were inflated by nearly 80%. The news is likely to anger advertisers who have spent money on videos based on predictions made using the overestimated viewing metrics. Publicis advertising group said that by Facebook introducing new “clearer” metrics, it was “coming up with new names for what they were meant to measure in the first place”. The advertising firm, who spent 77 billion US dollars on advertising last year, also added that the mistake “once again illuminated the absolute need to have 3rd party tagging and verification on Facebook”.