in the experimental group, compared to the control group who did not get the ads. In 2012 they also experimented with text message reminders to 180,000 people who had provided their mobile numbers. Texts the day before the election raised turnout six tenths of a percentage point, while texts on election day lowered turnout. Several mobile apps tell people where to vote, identify their elected officials, or search candidates' positions, though no evidence measures how much these raise turnout. Facebook apps let users see who their friends endorse, which gives them a shortcut in deciding whom to vote for. 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. Groups such as Postcards To Voters send handwritten postcards to potential voters ahead of elections in hopes of increasing turnout. A 2007 study showed that handwritten notes were three times as effective as machine-printed ones. See also Canvassing, an integral precursor to a GOTV operation Election campaigns Gevald campaign Issue advocacy List of democracy and elections-related topics Street money Voter registration in the United States References External links Tilting the Playing Field: Voter ID & Turnout US Federal and State Voter ID Requirements Election campaigning Political catchphrases