Researchers at the Cybersecurity for Democracy project at New York University found that politically extreme sources on Facebook tend to generate more interactions from users. Especially, posts from sources rated as far-right systematically received the highest engagement per follower of any partisan group. The researchers clarified that their study is limited due to the lack of data provided by Facebook. The company shares information about engagement but not impressions (how many people actually saw a piece of content and for how long). The researchers criticized Facebook for withholding data that is of public interest: the lack of transparency makes it impossible to dig deeper into the phenomenon.