[luu]

> Strange, nowhere in the article does it say how did they know that the views where inflated by 150 to 900%. How did they even know, without Facebook admitting it?

> I don't think they did

From the complaint at https://assets.documentcloud.org/documents/5004295/d5cb8373-...:

In September 2016, the Wall Street Journal revealed that, for the past two years, Facebook had been overstating the average time its users spent watching paid video advertisements. Based on information from advertising agencies who had spoken with Facebook, the Wall Street Journal reported that Facebook’s metrics had been overstated by between 60 and 80%. In response to the media attention, Facebook admitted it made a mistake, but emphasized that it had only discovered the mistake “about a month ago,” … Internal records recently produced in this litigation suggest, … Facebook did not discover its mistake one month before its public announcement. Facebook engineers knew for over a year, and multiple advertisers had reported aberrant results caused by the miscalculation (such as 100% average watch times for their video ads).

It seems that advertisers saw things that were obviously incorrect (e.g., 100% average watch times). Some kind of weirdness eventually led to a lawsuit. During the suit, the plaintiffs found evidence in internal documents that indicated that at least some engineers in Facebook knew there was a problem and maybe knew the magnitude of the problem. I wouldn't call that "Facebook admitting it". It sounds more like Facebook handed over some documents that they were legally obligated to hand over and then some lawyers read the documents.

If you're curious about the evidence, most of the court documents are public and available online, although the smoking gun on the percentage appears to be sealed.