Facebook became an incredibly successful advertising platform in part because it allows marketers to show people ads using fine-grained categories, which are generated based on an individual’s behavior. The company says this allows it to show users ads that are more relevant to their interests. But its data collection practices also have led to a series of privacy scandals over the past several years, along with increased scrutiny from lawmakers around the globe.

In response to questions about its targeting practices, Facebook has said that anyone can use the platform’s ad preferences menu to see and control how Facebook has categorized them. But a new survey from Pew Research Center suggests that the vast majority of US users isn't aware that Facebook tracks their interests and traits this way. When respondents found out, most said they were uncomfortable with the assumptions the social network had made.

The Numbers Last fall, Pew Research Center conducted a survey of Facebook users about the data Facebook collected on them. 74% of Facebook users said they did not know Facebook maintained a list of their interests

51% of users said they are not comfortable with Facebook compiling this information

27% of users said the list on their ad preferences page did not very or at all accurately represent them

From September 4 to October 1, Pew asked a nationally representative sample of 963 adult Facebook users to examine their “Your ad preferences” page, a menu where Facebook users can adjust ad-related privacy settings like third-party tracking. There, you can tell the social network to stop using your relationship status, employer, or where you went to school to target you with ads. If you don’t want to see ads for alcohol, children, or pets, this is also the place where you can tell Facebook that. In the Pew study, 74 percent of respondents said they didn’t know the page existed until they were directed to look at it. After being shown their ad preferences, 51 percent of respondents said they were not very or not at all comfortable with the fact that Facebook had created such a list of their traits and interests in the first place. Twenty-seven percent reported that the classifications were not accurate.

Facebook has emphasized repeatedly that its users can control how their personal data is used for targeted advertising. In a blog post from April last year in the wake of the Cambridge Analytica scandal, Rob Goldman, Facebook’s vice president of ads, mentioned the ad preferences page four different times. But even Facebook CEO Mark Zuckerberg has admitted that most Facebook users do not adjust the settings found there. “Some people use it. It’s not the majority of people on Facebook,” he said when he testified before the Senate’s Commerce and Judiciary committees that month.

“We want people to understand how our ad settings and controls work. That means better ads for people," Joe Osborne, a Facebook spokesperson, said in a statement. "While we and the rest of the online ad industry need to do more to educate people on how interest-based advertising works and how we protect people’s information, we welcome conversations about transparency and control.”1

“Your ad preferences” can be hard to understand if you haven’t looked at the page before. At the top, Facebook displays “Your interests.” These groupings are assigned based on your behavior on the platform and can be used by marketers to target you with ads. They can include fairly straightforward subjects, like “Netflix,” “Graduate school,” and “Entrepreneurship,” but also more bizarre ones, like “Everything” and “Authority.” Facebook has generated an enormous number of these categories for its users. ProPublica alone has collected over 50,000, including those only marketers can see.

According to Pew’s survey, 33 percent of US Facebook users said they were assigned 21 or more of these categories and 27 percent were given at least 10. Respondents who spent more time on Facebook or who had been using the service for longer reported that Facebook assigned them more topics. Fifty-nine percent of Pew’s participants reported the categories Facebook created for them correctly represented their interests, while 27 percent said the social network was not very or not at all correct in describing theirs.

How accurately Facebook characterized users’ traits appeared to be connected to how comfortable they are with the company’s practices: 78 percent of people who said the information was inaccurate were uncomfortable with their ad preferences, whereas only 48 percent who thought the information was correct felt the same way. Put another way, if you think Facebook has assumed something wrong about you, you’re more likely to feel uneasy about the fact that it’s making assumptions in the first place. (Eleven percent of respondents reported that they weren’t assigned any categories and told instead “You have no behaviors.”)