Facebook said a software bug went live in May that let repeat visits to online pages of companies or brands be counted as though someone new was taking a look each time Facebook on Wednesday said that it is working to fix flaws in its metrics calculations that led to the audience being overestimated at times.
It was the second time in months that Facebook acknowledged problems with assessing the reach of content at the leading online social network, a key factor in luring crucial advertising.
In September, Facebook said it had overestimated the average amount of time spent watching videos over the course of the previous two years.
Facebook said a software bug went live in May that let repeat visits to online pages of companies or brands be counted as though someone new was taking a look each time.
The software did not "de-duplicate" visits as intended, causing calculated averages for visits during seven- or 28-day periods to be inflated by 33 percent and 55 percent, respectively, according to Facebook
The social network also said that since August it has been overestimating by about seven percent the time spent on news stories published using its Instant Articles tool.
Facebook added that a stricter standard being used for tabulating when paid ads are viewed in news feeds at the social network was expected to reduce "reported reach" by an average of 20 percent.
On the other hand, Facebook said it had been undercounting the number of videos watched to completion, and expected a fix to boost that number by 35 percent.
The erroneous metrics were not those used to determine ad prices at the social network, according to Facebook.
However, the reach of content at Facebook is important to advertisers or companies when it comes to evaluating the potential impact of marketing campaigns.
The social network has an interest in maintaining advertiser confidence with reliable audience metrics. Facebook makes the bulk of its money from online advertising.
Facebook on Wednesday said it was taking steps to make information about its reach more reliable and transparent.
"We know that having access to reliable metrics is important to the millions of partners who use our services to grow their businesses," Facebook said in a blog post.
"As our products evolve to meet the needs of the people and businesses that use them, our metrics will also evolve."
Facebook also promised more collaborations with data-tracking companies such as comScore and Nielsen to ramp up third-party verification.
Explore further: Facebook apologizes to advertisers for counting error
