This is how Facebook knows where you’ve been and what you bought

Facebook gets data on individual users from many thousands of companies, and a new study (PDF) from Consumer Reports tried to put more exact numbers on it.

Researchers found that, on average, Facebook received data from 2,230 different companies for each of the 709 volunteers. One extreme example showed that “nearly 48,000 different companies were found in the data of a single volunteer.” In total, Facebook data archives showed that 186,892 companies had provided data on all of the study’s participants.

Volunteers recruited with help from The Markup pulled their personal data from Facebook using its Download Your Information tool and shared it with the researchers.

Companies using Meta’s advertising platform upload customers’ personal information and buying habits, which Meta uses to serve targeted ads to those people or people with similar profiles. The researchers believed that the ease of “microtargeting” campaigns to specific user data accounted for the fact that 96,000 of the companies listed were only targeting one of the volunteers.

Ninety-six percent of the study participants’ archives contained information shared by a data broker called LiveRamp, but it wasn’t all data brokers. Large retailers like The Home Depot, Walmart, or Amazon showed up, too, while other smaller businesses were “surprisingly well represented,” such as a car dealership in a 24,665-person town in Texas that covered 10 percent of the study’s volunteers on its own.

Most couldn’t be identified, though, as they used nonsense combinations of characters like “Bm 5 100tkqc nlm” or generic names like “Viking.” But the name doesn’t really matter, does it? Acxiom, the company that owns LiveRamp, says it can reach “over 2.5 billion of the world’s marketable consumers” and boasts about its “ability to build a complete view of the consumer for improved consumer recognition.”

We’ve all heard someone say our smartphones are listening to us, and that must be how they know which ads to show us. The truth is, companies aren’t just sitting around waiting for us to talk about jeans — they already know we want the jeans, what size we wear, which brands we like, and roughly what time of year we usually start buying them.