AboutTheData.com asks if you recognize your online self

Acxiom's AboutTheData.com lets you see and edit what marketers think they know about you.

For years now, "data brokers" have built billion-dollar businesses around collecting and selling information about you. They use public records, magazine subscriptions, online purchases, and surveys to construct individualized profiles on millions of Americans.

Now, one of these companies, Acxiom, will let you take a peek behind the curtain. Its website, AboutTheData.com, allows people to see what information Acxiom has collected and, if necessary, to correct the record.

"AboutTheData.com is the first step of a journey that will allow consumers more visibility and control into data about them," says Jennifer Barrett Glasgow, Acxiom's chief privacy officer, in an e-mail. "This is the first time any [data broker] has attempted this level of granularity at this scale."

Acxiom introduced the website just as the data-mining industry is reaching a crossroads. Thanks to online tracking, marketing firms can now gather information about individual consumers with unprecedented volume and accuracy, raising questions among legislators about whether these massive databases of biographical information should be more transparent.

Before you can log into AboutTheData.com, the site asks for your name, address, birthday, e-mail address, and the last four digits of your Social Security number. If it finds a match, Acxiom pulls up pages of data points: political leanings, race, number of children, household income, vehicle ownership, personal interests, and whether you use text messaging.

Many of these entries are simple guesses. Acxiom collects far more data than it can confirm. But by cross-referencing public records, warranty registrations, and retail history, the company can conclude with reasonable confidence whether someone rents or owns a home. Deciding whether an individual likes golf, however, takes a lot more conjecture.

"I was pegged as a motorcycling Christian who owns a Nissan Pathfinder and, I think, had two or three kids, all of which is entirely incorrect," says Jonathan Mayer, a junior affiliate scholar at Stanford University's Center for Internet and Society. "This certainly raises some questions about how useful is this really, if the data is so messy."

Acxiom encourages people to edit their profiles. As the data becomes more accurate, marketers will better understand which ads and offers are relevant to your interests.

Privacy advocates, on the other hand, worry that companies could abuse these databases – giving preferential treatment to high-value customers or targeting vulnerable consumers with predatory loans. Washington lawmakers have thrown around the idea of forcing all data brokers to disclose people's profiles, just as credit-rating agencies must by law offer consumers a free annual report.

Mr. Mayer thinks AboutTheData.com needs some work to be truly user-friendly, but he says it is a step in the right direction. People can suppress individual data points that they do not want marketers to know – or may opt out of Acxiom's system altogether. Of course, removing yourself from Acxiom's database does not scrub your name from the records of other digital marketing firms.

If you want greater privacy online, consider signing up for Do Not Track, a unified standard for privacy across each major Web browser. Several marketing firms and social networks, including Twitter and Pinterest, have agreed to not show targeted ads to people who have turned on this feature. You can learn more at DoNotTrack.us

For more on how technology intersects daily life, follow Chris on Twitter @venturenaut.