The term (PR) characterizes electoral systems by which divisions in an electorate are reflected proportionately in the elected body. If 30% of the electorate support a particular political party, then roughly 30% of seats will be won by that party. The essence of such systems is that votes contribute to the result, not just a plurality, or a bare majority, of them. Proportional representation requires the use of multiple-member voting districts (also called super-districts), it is not possible using single-member districts alone (but see biproportional apportionment). There are, basically, only two PR voting methods, party list PR and the single transferable vote (STV), but mixed member proportional representation (MMP), a hybrid method that uses party list PR as its proportional component, is also usually considered a distinct PR method. With party list PR, political parties define candidate lists, and voters vote for a list. The relative vote for each list determines how many candidates from each list are actually elected. Lists can be “closed” or “open”, open lists allowing voters to indicate individual candidate preferences and vote for independent candidates. Voting districts can be as large as a province or an entire nation. The single transferable vote uses smaller districts, voters ranking individual candidates in order of preference. During the count, as candidates are elected or eliminated, surplus or discarded votes that would otherwise be wasted are transferred to other candidates according to the preferences. STV enables voters to vote across party lines and to elect independent candidates. Mixed member proportional representation (MMP), also called the additional member system (AMS), is a hybrid, two-tier, system combining a non-proportional single-winner election and a compensatory regional or national party list PR one. Voters have two votes, one for their single-member district and one for the party list, the party list vote determining the balance of the parties in the elected body. Biproportional apportionment, first used in Zurich in 2006, is a two-tier method for adjusting an election’s result to achieve overall proportionality. A further system produces near perfect proportionality by dispensing with voting altogether: the random selection of representatives from the populace, known as sortition. It was used in ancient Athens and the Venetian Republic and is still used today in the summons to jury duty. In recent years, it has received increasing academic attention. Some form of proportional representation is used for national lower house elections in 94 countries, party list PR being the most widely used (85). MMP is used in seven lower houses, and STV, despite long being advocated by political scientists, is used in only two: Ireland, since independence in 1922, and Malta, since 1921; in the United States, party bosses were generally opposed to it because it transferred more power to the electorate when selecting independent candidates to put forward. As with all electoral systems, there are overlapping and contentious claims in terms of its advantages and disadvantages.