Proportional representation (PR) refers to any type of electoral system under which subgroups of an electorate are reflected proportionately in the elected body. The concept applies mainly to political divisions among voters. The essence of such systems is that all votes cast – or almost all votes cast – contribute to the result and are effectively used to help elect someone. Under other election systems, a bare plurality or a scant majority are all that are used to elect candidates. PR systems provide balanced representation to different factions, reflecting how votes are cast.
The electoral threshold, or election threshold, is the minimum share of votes that a candidate or political party requires before they become entitled to representation or additional seats in a legislature.
Single non-transferable vote or SNTV is an electoral system used to elect multiple winners. It is a semi-proportional variant of first-past-the-post voting, applied to multi-member districts where each voter casts just one vote. SNTV generally makes it unlikely that a single party will take all seats in a city, as generally happens with winner-take-all systems. SNTV can be considered a variant of dot voting where each voter has only one point to assign.
In the study of electoral systems, the Droop quota is the minimum number of supporters a party or candidate needs to receive in a district to guarantee they will win at least one seat in a legislature.
The D'Hondt method, also called the Jefferson method or the greatest divisors method, is an apportionment method for allocating seats in parliaments among federal states, or in proportional representation among political parties. It belongs to the class of highest-averages methods. Compared to ideal proportional representation, the D'Hondt method reduces somewhat the political fragmentation for smaller electoral district sizes, where it favors larger political parties over small parties.
The Webster method, also called the Sainte-Laguë method, is a highest averages apportionment method for allocating seats in a parliament among federal states, or among parties in a party-list proportional representation system. The Sainte-Laguë method shows a more equal seats-to-votes ratio for different sized parties among apportionment methods.
The Gallagher index measures an electoral system's relative disproportionality between votes received and seats in a legislature. As such, it measures the difference between the percentage of votes each party gets and the percentage of seats each party gets in the resulting legislature, and it also measures this disproportionality from all parties collectively in any one given election. That collective disproportionality from the election is given a precise score, which can then be used in comparing various levels of proportionality among various elections from various electoral systems. The Gallagher index is a statistical analysis methodology utilised within political science, notably the branch of psephology.
The single transferable vote (STV) is a proportional representation system that elects multiple winners. It is one of several ways of choosing winners from ballots that rank candidates by preference. Under STV, an elector's vote is initially allocated to their first-ranked candidate. Candidates are elected (winners) if their vote tally reaches quota. After the winners in the first count are determined, if seats are still open, surplus votes — those in excess of an electoral quota— are transferred from winners to the remaining candidates (hopefuls) according to the surplus ballots' next usable back-up preference.
The Pedersen index is a measure of political volatility in party systems. It was described by Mogens Pedersen in a paper published in 1979 entitled The Dynamics of European Party Systems: Changing Patterns of Electoral Volatility.
The cube rule or cube law is an empirical observation regarding elections under the first-past-the-post system. The rule suggests that the party getting the most votes is over-represented. It was first formulated in a report on British elections in 1909, then extended to elections in other countries. Both in theory and in practice, the cube rule is only applicable in a two-party system. In a multi-party democracy operating under the first-past-the-post system, the cube law invariably fails, often leading to capricious results.
In proportional representation systems, an electoral quota is the number of votes a candidate needs to be guaranteed election. They are used in some systems where a formula other than plurality is used to allocate seats.
Matthew Søberg Shugart is an American political scientist. He is a Distinguished Professor of political science at the University of California, Davis. He is also an Affiliated Professor at the University of Haifa. Shugart specializes in electoral systems, party systems, and the design of political institutions, primarily through empirical studies of political systems across large numbers of countries. Shugart is also an orchardist, and runs the Fruits and Votes blog on electoral systems and fruit growing.
In voting theory, the micromega rule holds that, when political parties choose electoral systems, "the large prefer the small and the small prefer the large". The term "micromega" references Micromégas, a tale by Voltaire in which dwarfs and giants dialogue.
Party-list representation in the House of Representatives of the Philippines refers to a system in which 20% of the House of Representatives is elected. While the House is predominantly elected by a plurality voting system, known as a first-past-the-post system, party-list representatives are elected by a type of party-list proportional representation. The 1987 Constitution of the Philippines created the party-list system. Originally, the party-list was open to underrepresented community sectors or groups, including labor, peasant, urban poor, indigenous cultural, women, youth, and other such sectors as may be defined by law. However, a 2013 Supreme Court decision clarified that the party-list is a system of proportional representation open to various kinds of groups and parties, and not an exercise exclusive to marginalized sectors. National parties or organizations and regional parties or organizations do not need to organize along sectoral lines and do not need to represent any marginalized and underrepresented sector.
The Loosemore–Hanby index measures disproportionality of electoral systems, how much the principle of one person, one vote is violated. It computes the absolute difference between votes cast and seats obtained using the formula:
Apportionment in the Hellenic Parliament refers to those provisions of the Greek electoral law relating to the distribution of Greece's 300 parliamentary seats to the parliamentary constituencies, as well as to the method of seat allocation in Greek legislative elections for the various political parties. The electoral law was codified for the first time through a 2012 Presidential Decree. Articles 1, 2, and 3 deal with how the parliamentary seats are allocated to the various constituencies, while articles 99 and 100 legislate the method of parliamentary apportionment for political parties in an election. In both cases, Greece uses the largest remainder method.
The cube root law is an observation in political science that the number of members of a unicameral legislature, or of the lower house of a bicameral legislature, is about the cube root of the population being represented. The rule was devised by Estonian political scientist Rein Taagepera in his 1972 paper "The size of national assemblies".
Grigorii Vasilyevich Golosov, sometimes spelled as Grigory Golosov, is a Russian political scientist. He is a professor and the Head of Political Science Department at the European University at Saint Petersburg, Russia. He is notable as expert on political institutions and electoral systems, in particular, in application to Russia. His article "Electoral Systems and Party Formation in Russia" received a Lawrence Longley Award of the American Political Science Association for the best journal article on electoral systems and representation published in 2003.
The 2005 Devon County Council election was an election to Devon County Council which took place on 5 May 2005 as part of the 2005 United Kingdom local elections. 62 councillors were elected from various electoral divisions, which returned either one or two county councillors each by first-past-the-post voting for a four-year term of office. The electoral divisions had been redrawn since the last election in 2001. No elections were held in Plymouth and Torbay, which are unitary authorities outside the area covered by the County Council.
Political fragmentation is the division of the political landscape into different parties and groups. Political fragmentation can apply to political parties, political groups or other political organisations. It is most often operationalized using the effective number of parliamentary parties.
