Shares of the company were down 4.1 percent at $179.25 after the bell.
The changes have reduced the amount of time spent on the site by about 50 million hours a day, he added.
Facebook identifies local publishers "as those that are clicked on by readers in a tight geographic area".
The stock fell 5% in after-hours trading following the report, a rare decline for a company that consistently outpaces Wall Street's estimates. The S&P 500 Index .SPX rose 24 percent during the same period.
But the comment underscores the hard situation Facebook finds itself in, as its social network has come under fire for spreading misinformation and propaganda, as well as for incentivizing consumers to spend too much time on its site.
Freeport-McMoran, Inc. (NASDAQ:FCX) To Report Earnings
The stock witnessed 91.32% gains, 93.09% gains and 114.18% gains for the 1-month, 3-month and 6-month period, respectively. The analysts, on average, are forecasting a $17.89 price target, but the stock is already up 77.38% from its recent lows.
We've worked closely with local publishers through the Facebook Journalism Project over the a year ago, visiting newsrooms around the world to provide training and support for journalists, as well as building products that work for their publications and readers.
The first changes will be applied to the News Feed where users will see more updates from friends, family and groups. But such changes come at a cost. "But I also expect the time you do spend on Facebook will be more valuable", he wrote.
For now, Facebook continues to be an ad sales juggernaut. The spending spree includes new warehouses full of servers and thousands of new workers to review content posted by users.
Diluted earnings per share were $1.44, up from $1.21 a year ago. Without the adjustment, Facebook would have earned $2.21, topping consensus of $1.94. Monthly active users were 2.13 billion, compared to 1.86 billion 12 months earlier.
The technology firm reported a 47% increase in revenue on the same period a year ago in its latest quarterly financial results. That's despite the fact that Facebook once again had a blockbuster year in 2017: The company revealed Wednesday that it generated $40.65 billion in revenue in 2017, compared to $26.89 billion in 2016. Mobile advertising revenue now makes up 89 percent of overall ad revenue, up from 84 percent a year prior.
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