 According to a 2012 study, 24% of the voting-eligible population in the United States are not registered to vote, equaling some 51 million U.S. citizens.While voters traditionally had to register at government offices by a certain period of time before an election, in the mid-1990s, the federal government made efforts to facilitate registering, in an attempt to increase turnout.The National Voter Registration Act of 1993 (the "Motor Voter" law) now requires state governments to "either" provide uniform opt-in registration services through drivers' license registration centers, disability centers, schools, libraries, and mail-in registration, "or" to allow Election Day voter registration, where voters can register at polling places immediately prior to voting.