Ooh, Facebook is in trouble again.

You see, for two years the social network has “vastly overestimated average viewing time for video ads on its platform,” according to The Wall Street Journal, and now big ad buyers and marketers are really upset.

Here’s how it came out:

Several weeks ago, Facebook disclosed in a post on its “Advertiser Help Centre” that its metric for the average time users spent watching videos was artificially inflated because it was only factoring in video views of more than three seconds. The company said it was introducing a new metric to fix the problem.

Some ad agencies, however, were informed about the metric change by Facebook directly.

Ad buying agencies Publicis Media and GroupM (the ad buying unit of WPP Plc) were told by the social media platform that the earlier counting method “overestimated average time spent watching videos by between 60% and 80%.”

Publicis was responsible for purchasing roughly $77 billion in ads on behalf of marketers around the world in 2015, according to estimates from research firm RECMA.

In recent years, Facebook has been on a mission to sell the growth of video consumption and now, because of the miscalculated data, marketers may have misjudged the performance of video advertising they have purchased from Facebook over the past two years.

This, in effect, could lead advertisers back to other platforms like YouTube, Twitter, and even, gasp!, television.

Here’s what Facebook did:

For the past two years Facebook only counted video views of more than three seconds when calculating its “Average Duration of Video Viewed” metric.

Video views of under three seconds were not factored in, thereby inflating the average. Facebook’s new metric, “Average Watch Time”, will reflect video views of any duration. That will replace the earlier metric.

In a letter Publicis sent to its clients, it said:

This once again illuminates the absolute need to have 3rd party tagging and verification on Facebook’s platform. Two years of reporting inflated performance numbers is unacceptable.

To be fair, while Facebook users are on the rise, it’s more important than ever to provide the most transparent service to your users as possible, whether they are businesses or people.

[source:wsj]