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Russian trolls who tried to influence the 2016 U.S. election had more success reaching American users on Instagram than many realized.

An independent study from New Knowledge, which examined the posts and ads shared on social media by Russia’s Internet Research Agency, found that while the Instagram posts in question reached fewer people than the Facebook posts, people interacted much more with the posts on Instagram.

Content that was shared to Facebook led to 76.5 million “engagements,” action from users like comments, shares and “Likes.” On Instagram — where there is no sharing feature — posts from the IRA generated more than 187 million engagements from “Likes” and comments alone, almost 2.5 times as many interactions.

“Instagram was perhaps the most effective platform for the Internet Research Agency,” the report concluded. Roughly 40 percent of the Instagram accounts created by the IRA reached 10,000 followers, a threshold that New Knowledge said qualified as being a “micro-influencer” — a social media account that has a substantial and engaged following, but is not a household name.

The new report — plus a separate report from the University of Oxford also released Monday — provides a fresh look at how social platforms were unwittingly used to influence voter opinion ahead of the 2016 election.

A lot of the conclusions are familiar, though Instagram’s influence stood out, in part because the platform has largely been overshadowed by the role that its parent company, Facebook, also played in the election.

Facebook may have reached more people — 126 million people compared to Instagram’s estimated 20 million — but advertisers will tell you that engagement matters a lot. Taking the time to “Like” or comment usually means people absorbed whatever it is they looked at. Instagram, we are now learning, may have enabled the IRA to land its messaging better than any other service.

The report included other interesting elements, some of them previously known. The IRA crafted social media campaigns around hot-button social issues, like the Black Lives Matter movement, and posted more support for then-presidential candidate Donald Trump and more criticism of then-candidate Hillary Clinton. Both of these revelations have been widely reported.

But the report also found that the IRA specifically targeted its message to African American voters and encouraged more liberal voters to avoid voting altogether. Here’s how New Knowledge, a cybersecurity company, explained it in the report:

In the days leading up to the election, the IRA began to deploy voter suppression tactics on the Black-community targeted accounts, while simultaneously fearmongering on Right-targeted accounts about voter fraud and delivering ominous warnings that the election would be stolen and violence might be necessary. The suppression narratives were targeted almost exclusively at the Black community on Instagram and Facebook.

What’s still unknown is what impact these reports might have on the tech companies that own these platforms, such as Facebook, Twitter and Google. Some in Congress have used what happened leading up to the election to call for more tech regulation, and Sen. Mark Warner of Virginia, one of tech’s most vocal critics and a member of the Senate Intelligence Committee, repeated that call Monday.

“This should stand as a wake-up call to us all that none of us are immune from this threat, and it is time to get serious in addressing this challenge,” he said in a statement. “That is going to require some much-needed and long-overdue guardrails when it comes to social media.”

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