Facebook obtains personal user data from thousands of companies, and a new study (PDF) from Consumer Reports attempts to get a more precise count. Researchers found that across 709 volunteers, Facebook obtained personal data from an average of 2,230 different companies. An extreme example shows that "nearly 48,000 different companies were found in one volunteer's data."

Facebook's data archives show that a total of 186,892 companies provided data on all study participants.

Volunteers recruited with the help of TheMarkup used the Download Your Info tool to extract their personal data from Facebook and share it with researchers.

An infographic shows how information travels from individuals to their apps, servers, and to Facebook, which uses the information to serve ads to users.

Companies using the Meta advertising platform upload customers' personal information and purchasing habits, and Meta uses this information to serve targeted ads to these people or people with similar characteristics, because it is so easy to conduct "micro-targeting" campaigns against specific user data.

The infographic shows how businesses work with data brokers who aggregate personal information from multiple sources before providing it to Facebook for ad targeting.

96% of study participants' profiles included information shared by a data broker called LiveRamp, but it wasn't all data broker information. Large retailers like Home Depot, Walmart or Amazon are also present, while other small businesses are also "surprisingly numerous", such as a car dealer in a Texas town of 24,665 people, which itself reached 10% of the volunteers in the study.

However, most businesses are unrecognizable because they use meaningless character combinations like "Bm5100tkqcnlm" or generic names like "Viking." But the name doesn't matter. LiveRamp's owner, Acxiom, says it has access to "more than 2.5 billion marketable consumers worldwide" and boasts of its "ability to build a complete consumer view and improve consumer identification." Now it seems they weren't bragging.

We've all heard it said that our smartphones listen to us so they know which ads to show us. The truth is, companies aren't waiting for us to talk about jeans—they already know what we want in jeans, what size we wear, which brands we like, and even roughly what time of year we start buying jeans.