A data-driven campaign is no campaign at all without up-to-date information. So how does a national campaign work to update its supporter address database? Give away something free.

President Barack Obama’s re-election campaign blasted a message to supporters Thursday offering them a free Obama 2012 bumper sticker. The rationale for the giveaway, according to Jeremy Bird, the campaign’s national field director, is increasing the campaign’s visibility and updating its database of supporter addresses.

“When you sign up to get one, you’re also making sure we have your most recent contact information,” Bird wrote in the email. “We’re  running this campaign at the local level, and we can’t keep you up to date on the best ways to get involved in your area if we’ve got your old address on file.”

In 2008, the Obama campaign used its vast email and telephone list to keep supporters informed and help get out the vote. The email list reportedly stood at 13 million at the end of the campaign.