Yes – in more ways than you think. Your level of education, ethnicity, whether you own a home, relationship status, birthday, job, political views, car, internet browser, investments and TV habits are just some of the types of data that can be used.

Awareness about how social media companies are using personal information has been heightened by the scandal surrounding Cambridge Analytica and Facebook. The political consulting firm harvested the data of at least 87 mln people after launching an app where hundreds of thousands of people were paid to take a personality test. Participants gave consent for their data to be collected – but the details of their friends were also harvested without their knowledge.

Facebook CEO Mark Zuckerberg faced questions in Congress about the controversy. He denied that the social network sells personal data to advertisers, but said: “What we allow is for advertisers to tell us who they want to reach, and then we do the placement.”

In 2017, the social network generated almost $40 bln in revenue from advertising – a 49 percent increase on the year before.