Attention, digital publishers and advertisers: Facebook has checked its math again. It needs to make some corrections.
The social network says it has been miscalculating several of the metrics it uses to measure how content performs on its property. It says the new numbers may differ significantly from what publishers are used to seeing.
In one case, a metric that measures how many people can see a publisher's content on its page may shrink by 55 percent.
Facebook's do-over comes a couple months after the company made a similar report, when it announced it had been overestimating a video viewing metric.
That disclosure prompted a flurry of discussion over whether publishers and advertisers could trust the data they were getting from one of the two dominant players in digital media. This news should do the same.
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In both cases, Facebook says none of the restated numbers should affect the results advertisers paid for. If you gave Facebook money to generate a certain number of clicks or impressions, Facebook still delivered what you paid for, says Facebook ad boss Carolyn Everson.
Everson says that after Facebook disclosed that its video viewing numbers were off, it went back and reviewed other metrics, which led to the changes it's announcing today.
The biggest change is to metrics that measured how many people could see a publisher's Facebook page over the course of a week and a month; those numbers may shrink by an average of 33 percent and 55 percent, Facebook says.
But Facebook says it has been correctly measuring how many people could see a publisher's page on a daily basis, how individual posts performed and what happens when publishers pay Facebook to reach more people.
At the same time, the company is announcing other changes meant to give advertisers more confidence, including giving third-party auditors like ComScore, Nielsen and Moat more access to Facebook's data.
"We are committed to doing what we need to do to provide the industry with more clarity, and give the industry more confidence in our metrics," Everson said. "We have an unwavering commitment to getting this right at any given moment, knowing that it is going to continue to evolve."
Everson says Facebook's erroneous metrics are the results of bugs in their calculations, not a flaw in Facebook's methodology.
In one case, Facebook's new math will increase the results publishers are used to seeing: Facebook says the metric that tracks how many people watched 100 percent of a video may grow by 35 percent.
—By Peter Kafka, Recode.net.
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