The new feature, called "story bumping," allows organic stories that you did not scroll far enough to see to reappear near the top of your News Feed as long as the posts are getting lots of likes and comments.
According to Lars Backstrom, an engineering manager at Facebook, the company tested story bumping with a small group of users. The result was a 5% increase in the number of likes, comments and shares on the organic stories people saw from friends and an 8% increase in likes, comments and shares on the organic stories they saw from Pages.
Story bumping also increased the number of posts Facebook users read: Previously, users read 57% of the posts in their News Feeds. When unread stories were resurfaced, that number increased to 70%, Backstrom said in a blog post.
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"The data suggests that this update does a better job of showing people the stories they want to see, even if they missed them the first time," Backstrom said. "For Page owners, this means their most popular organic Page posts have a higher chance of being shown to more people, even if they're more than a few hours old."
Ari Rosenstein, VP of marketing at advertising company Adotomi, said that this could push advertisers to change their focus.
"News Feed improvements such as story bumping are going to make News Feed content even more targeted and relevant for users, which is a great benefit," he said. "Advertisers should look to focus more on ads in the News Feed and less on Page posts to Fans. [News Feed] ads will allow for better targeting, larger reach, and the ability to better control the duration of the message."
Although Facebook's algorithm has been controversial, the social network stands by its necessity. As the volume of content in users' News Feeds has increased -- on average, 1,500 posts from friends and pages every time a user visits the site -- the need for a method to show what matters most was necessary, Backstrom said.
The algorithm takes into account your actions on the social network. In general, it notes how often you interact with a friend, Page or public figure; the number of likes, shares and comments a post receives from the public and your friends in particular; how much you've interacted with this type of post in the past; and whether you and others are hiding or reporting a particular post, Facebook said. Each of these interactions are ranked to determine where a post appears in your News Feed.
"With so many stories, there is a good chance people would miss something they wanted to see if we displayed a continuous, unranked stream of information," Backstrom said. "Our ranking isn't perfect, but in our tests, when we stop ranking and instead show posts in chronological order, the number of stories people read and the likes and comments they make decrease."
Another change Facebook made to the news feed is called "last actor." This bumps up content from someone you have recently interacted with -- for example, liking one of their photos or commenting on one of their posts. "Last actor" takes into account the last 50 interactions you've had with content.