Studies in 2012 and 2017 found that Facebook's "I'm Voting/I'm a Voter" button increased turnout in the 2010 Congressional elections by six tenths of a percentage point, and in the 2012 presidential election by a quarter of a percentage point. It named their friends who had clicked the voting button, thus opting in and minimizing complaints. However the button only appeared on election day, so it did not let friends track and encourage each other throughout the early voting period which most states have. It has been used in many elections throughout the world since then, without clarity on which users see it, leading to concerns on how it biases turnout.