As Americans were leave their polling stations Tuesday, many donned “I voted” stickers to show others they cast their ballot. Many businesses offered free food, drinks or services to people who were wearing their stickers, but how the custom was born remains a mystery. According to Time magazine, the stickers likely became popular in the 1980s, citing a 1982 article in the Miami Herald newspaper as the first time the stickers were mentioned in the press. Election supply vendor Intab, said it designed a version of the stickers in 1987 because, according to Janet Boudreau, who used to run the company, the stickers served as a reminder that it was Election Day. “I wanted them to see people with an ‘I Voted’ sticker and think, ‘Oh, I should do that,'” she told Time. It remains debatable if the sticker actually drives more people to the polls, but according to Richard Bensel, professor of government at Cornell University and author of The American Ballot Box in the Mid-Nineteenth Century, the stickers may help foster a sense of community around voting. There is also some evidence supporting the theory that people are more likely to cast their vote if they think someone may ask them about it. For example, researchers from the University of California-Berkeley, the University of Chicago, and Harvard University found recently that “telling people they’re going to be asked about voting will make them more likely to vote.” For some, the stickers serve as a kind of thank you for voting, something Costas Panagopoulos, a professor of political science at Fordham University said will make them likely to vote again. “People who get the sticker have already voted, so they’re motivated enough for it to have worked in the first place,” he says. “If we could find the people who didn’t vote and give them a sticker saying ‘I Didn’t Vote,’ that could cause a greater increase in turnout.” But the popularity of the stickers may be waning. For example, in Santa Clara, California, officials said they saved $90,000 not ordering the stickers in 2012, and other precincts have stopped handing them out to stop people from sticking them to public places. But it didn't stop many during primary elections earlier this year from placing their stickers on the tombstone of suffragist Susan B. Anthony and slavery abolitionist Harriet Tubman.