Facebook admits miscalculating more ad metrics

What a tough year for the social network giant.

Following the stock market plunge after Donald Trump's victory, and the scrutiny on Facebook for influencing the presidential election with fake news (Read more: Google and Facebook to cut ad revenue to sites pushing ‘fake news’), as well as violating anti-discrimination laws with one of its tools (Read more: Facebook to stop ads from targeting users by race), the social network has just admitted in a blog post that it messed up more ad metrics than previously thought.

In its latest blog post, Facebook said it discovered miscalculations on the number of completed video views, the total organic reach for business Pages, and the amount of time spent with Instant Articles.

The average time spent on Instant Articles was "over-reported" by 7% - 8% since August, 2015 due to "a calculation error": Facebook was calculating the average across a histogram of time spent, instead of reflecting the total time spent reading an article divided by its total views. "We have now fixed this issue," said Facebook.

The company also overestimated the number of people businesses reached with unpaid posts on their Facebook Pages during the preceding week and month, because it forgot to de-duplicate repeat visitors, hence, it doubled-count.

"This bug has been live since May; we will be fixing this in the next few weeks," Facebook said, adding that it does not affect paid reach.

Two months ago, Facebook apologised for "overstating" the average time users spend watching videos.

This latest admission may once again renew concerns about whether its math and metrics are reliable for marketers and publishers, but Facebook  has said it will disclose further updates on a new blog that's specifically dedicated to metrics news.

Facebook said none of the issues would affect client billing.