Terry Parris

Imagine if, during the Jim Crow era, a newspaper offered advertisers the option of placing ads only in copies that went to white readers. That’s basically what Facebook is doing nowadays.

The ubiquitous social network not only allows advertisers to target users by their interests or background, it also gives advertisers the ability to exclude specific groups it calls “Ethnic Affinities.” Ads that exclude people based on race, gender and other sensitive factors are prohibited by federal law in housing and employment. The ad we purchased was targeted to Facebook members who were house hunting and excluded anyone with an “affinity” for African-American, Asian-American or Hispanic people. When we showed Facebook’s racial exclusion options to a prominent civil rights lawyer John Relman, he gasped and said, “This is horrifying. This is massively illegal. This is about as blatant a violation of the federal Fair Housing Act as one can find.”

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.