We’ve spent a lot of time this past year trying to understand how the National Security Agency gathers and stores information about ordinary people. But there’s also a thriving public marketfor data on individual Americans-especially data about the things we buy and might want to buy.

Consumer data companies are scooping up huge amountsof consumer information about people around the world and selling it, providing marketers details about whether you’re pregnant or divorced or trying to lose weight, about how rich you are and what kinds of cars you drive. But many people still don’t know data brokers exist.

The Federal Trade Commission is pushing the companies to give consumers more information and control over what happens to their data. The White House released a report this May outlining concerns that these detailed consumer profiles might lead to race or income-based discrimination-what the White House called “digital redlining.”

It’s very hard to tell who is collecting or sharing your data-or what kinds of information companies are collecting. Early this year, Office Max sent a letter to a grieving father addressed to his name, followed by “daughter killed in car crash.”

Here’s a look at what we know-and what we don’t-about the consumer data industry.

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