What Facebook Knows About You

We live in an era of increasing automation. Machines help us not only with manual labor but also with intellectual tasks, such as curating the news we read and calculating the best driving directions. But as machines make more decisions for us, it is increasingly important to understand the algorithms that produce their judgments. We’ve spent the year investigating algorithms, from how they’ve been used to predict future criminals to Amazon’s use of them to advantage itself over competitors. All too often, these algorithms are a black box: It’s impossible for outsiders to know what’s going inside them. Sept 28 we’re launching a series of experiments to help give you the power to see inside. Our first stop: Facebook and your personal data.

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.