Compulsory voting
Compulsory voting is an effect of laws which require eligible citizens to register and vote in elections, and may impose penalties on those who fail to do so. , 22 countries provide for compulsory voting, and 11 democracies — about 5% of all United Nations members — enforce it.
Contingent vote
Today, a special variant of the contingent vote is used to elect the President of Sri Lanka. Another variant, called the supplementary vote, is used to elect mayors and Police and Crime Commissioners in England. In the past the ordinary form of the contingent vote was used to elect the Legislative Assembly of Queensland from 1892 to 1942. To date, this has been the longest continuous use of the system anywhere in the world. It was also used in the US state of Alabama in the 1920s.