Facebook pages run by local law enforcement agencies significantly overrepresented Black suspects, and those practices reinforce racial stereotypes about crime, a new study suggests.

Why it matters: The social media platform with more than a billion users makes it easy to reshare police posts that critics say can distort people's understanding of local crime.

Details: A study published last week in the journal Proceedings of the National Academy of Sciences analyzed nine years of posts on the Facebook pages of nearly 14,000 local police departments.

• Altogether, researchers found about 100,000 posts that mentioned the ethnicity of a suspect in a crime. Roughly 32% of those posts mentioned a Black person.
• But Black people represented just 20% of the people those departments ultimately arrested.
• And those posts were shared widely, leading to an even bigger discrepancy when comparing arrest rates to how many people saw a post that singled out a Black suspect.
• "Most of the country was exposed to overreporting on Black suspects," the report said.

What they're saying: "The local news stations are getting their news directly from the Facebook pages of these agencies," John Rappaport, a professor at the University of Chicago Law School and one of the authors of the report, told Axios.

• "You can see the same language. They just cut and paste the language into the news stories."
• Rappaport said studies show that as people are exposed to more stories about Black people and crime, they become more biased.

"We seem to have this assumption that crime reports should have race descriptions in them and we're not questioning it," said Julian Nyarko, Assistant Professor of Law at Stanford Law School and another author of the report.

• "Part of our message is to point out there is a very significant social cost which is the stigmatization." 

The intrigue: The study constructed its Facebook dataset using CrowdTangle, a website that tracks interactions on public content from Facebook pages and groups. Facebook runs CrowdTangle.

The other side: The Fraternal Order of Police, the largest organization of law enforcement officers, did not respond to a request for comment.

• "Our mission is to aid in the projection of transparency for the Chicago Police Department by professional and accurate communications with local and national media outlets, as well as the community," Chicago police spokesperson Tom Ahern told Axios.
• "We use social media to enhance the image of CPD and to provide important information by communicating or assisting in the dissemination of critical information in a timely manner."

Between the lines: The onus is on the journalism organizations to approach police departments' Facebook pages with some skepticism and do additional reporting, Michael V. Marcotte, a professor of practice in the Communication & Journalism Department at the University of New Mexico, told Axios.

The bottom line: Researchers said police need to reconsider when they use the race of a suspect in a post, and that reporters should think twice about using race or resist to cut and paste posts into stories without follow-up phone calls.