All too often, these algorithms are a black box: It’s impossible for outsiders to know what’s going inside them.
Facebook has a particularly comprehensive set of dossiers on its more than 2 billion members. Every time a Facebook member likes a post, tags a photo, updates their favorite movies in their profile, posts a comment about a politician, or changes their relationship status, Facebook logs it. When they browse the Web, Facebook collects information about pages they visit that contain Facebook sharing buttons. When they use Instagram or WhatsApp on their phone, which are both owned by Facebook, they contribute more data to Facebook’s dossier.
And in case that wasn’t enough, Facebook also buys data about its users’ mortgages, car ownership and shopping habits from some of the biggest commercial data brokers.
Facebook uses all this data to offer marketers a chance to target ads to increasingly specific groups of people. Indeed, we found Facebook offers advertisers more than 1,300 categories for ad targeting — everything from people whose property size is less than .26 acres to households with exactly seven credit cards.
We built a tool that works with the Chrome Web browser that lets you see what Facebook says it knows about you — you can rate the data for accuracy and you can send it to us, if you like. We will, of course, protect your privacy. We won’t collect any identifying details about you. And we won’t share your personal data with anyone.
Watch the video series at: https://www.propublica.org/article/breaking-the-black-box-what-facebook-knows-about-you.