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The binomial system () is a
voting system An electoral or voting system is a set of rules used to determine the results of an election. Electoral systems are used in politics to elect governments, while non-political elections may take place in business, nonprofit organizations and inf ...
that was used in the legislative elections of Chile between 1989 and 2013. The binomial system is the
D'Hondt method 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 ...
with an
open list Open list describes any variant of party-list proportional representation where voters have at least some influence on the order in which a Political party, party's candidates are elected. This is as opposed to closed list, in which party lists ...
where ''every'' constituency returns ''two'' (hence the name) representatives to the legislative body. The fact that only two candidates are elected in each district results in the peculiarity where the second most supported list is over-represented. Its use was prescribed in the respective constitutional organic law during the
Pinochet regime An authoritarian military dictatorship ruled Chile for seventeen years, between 11 September 1973 and 11 March 1990. The dictatorship was established after the Presidency of Salvador Allende, democratically elected socialist government of Salv ...
. The binomial system was invented in
Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...
in the 1980s under the
Wojciech Jaruzelski Wojciech Witold Jaruzelski ( ; ; 6 July 1923 – 25 May 2014) was a Polish military general, politician and ''de facto'' leader of the Polish People's Republic from 1981 until 1989. He was the First Secretary of the Polish United Workers' Party ...
regime, in order to foster political stability in the democratization process, maintaining the preeminence of the
Polish United Workers' Party The Polish United Workers' Party (, ), commonly abbreviated to PZPR, was the communist party which ruled the Polish People's Republic as a one-party state from 1948 to 1989. The PZPR had led two other legally permitted subordinate minor parti ...
against the rise of the opposition movement ''
Solidarity Solidarity or solidarism is an awareness of shared interests, objectives, standards, and sympathies creating a psychological sense of unity of groups or classes. True solidarity means moving beyond individual identities and single issue politics ...
'', being recognized as a system that promoted consensus and negotiation between opposing sides of government. The binomial system was considered by most analysts as the main constitutional lock that prevented completion of the
Chilean transition to democracy The military regime in Chile led by General Augusto Pinochet ended on 11 March 1990 and was replaced by a democratically elected government. The transition period lasted roughly two years, although some aspects of the process lasted significan ...
.


Name and similar methods

The term binomial system refers to the dual-member districts the system uses. Within these districts, the
apportionment The legal term apportionment (; Mediaeval Latin: , derived from , share), also called delimitation, is in general the distribution or allotment of proper shares, though may have different meanings in different contexts. Apportionment can refer ...
method (between parties, not candidates) is technically proportional, but because of the small district magnitude it is across the whole assembly, semi-proportional. In practice, because there are only two seats and Chile operates under a
two-party system A two-party system is a political party system in which two major political parties consistently dominate the political landscape. At any point in time, one of the two parties typically holds a majority in the legislature and is usually referr ...
, the rule behaves like a power-sharing agreement where the two major parties each take maximum half the seats in the legislature (unless in enough districts the larger party can win with a landslide - in this case double the number of votes as the runner-up party). The binomial system is also distinct from
biproportional apportionment Biproportional apportionment is a proportional representation method to allocate seats in proportion to two separate characteristics. That is, for two different partitions each part receives the proportional number of seats within the total numb ...
, despite the similarity in name, although it is technically proportional both geographically and within districts, biproportional systems used a unified
algorithm In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...
for determining how many seats each region gets and to achieve party proportionality on the whole, based on the votes cast. It is also not to be confused with the dual-member mixed proportional (DMP) system, often shortened to dual-member proportional, a system invented in 2013 (the same year the binomial system was abolished in Chile). This method is different from the binomial system, being a
mixed system A mixed electoral system is one that uses different electoral systems to elect different seats in a legislature. Most often, this involves a First Past the Post combined with a proportional component. The results of the combination may be mixed- ...
which provides
mixed-member proportional representation Mixed-member proportional representation (MMP or MMPR) is a type of representation provided by some mixed electoral system, mixed electoral systems which combine local Winner-take-all system, winner-take-all elections with a Compensation (el ...
by allocating the first seat by
plurality Plurality may refer to: Law and politics * Plurality decision, in a decision by a multi-member court, an opinion held by more judges than any other but not by an overall majority * Plurality (voting), when a candidate or proposition polls more ...
, and the second within the compensation mechanism (based on the national or regional popular vote). Under DMP, a voter can vote for pairs of candidates on their ballot, functioning as a
closed list Closed list describes the variant of party-list systems where voters can effectively vote for only political parties as a whole; thus they have no influence on the party-supplied order in which party candidates are elected. If voters had some in ...
locally, but as a best loser system for compensation.


Characteristics

The system works in the following manner: Parties and independent candidates group themselves into lists or coalitions, basically electoral blocs. Each list proposes up to two candidates per electoral region, province, or other geographical unit. Votes are first tallied by list instead of by candidate, and unless the list which obtained a majority has double the voting as the second most supported list, each of the two lists gets one of their candidates, the one who got the most voting, into office. In other words, the binomial system basically means that the first (absolute or relative majority i.e.:
plurality Plurality may refer to: Law and politics * Plurality decision, in a decision by a multi-member court, an opinion held by more judges than any other but not by an overall majority * Plurality (voting), when a candidate or proposition polls more ...
) and the second largest party get equal representation unless the majority doubles the second. For example, in the following cases the candidate that would get elected under a binomial system are marked with an The most common case is Case 2, in which one list gets a total voting that is higher than the other but both get exactly the same number of candidates elected, candidates 1A and 2A respectively. In the unlikely case that both lists get exactly the same number of votes each gets a candidate into office. Only in the case that List 1 doubles the voting of List 2 will List 1 be able to get two seats, even if, like in Case 3, the second elected candidate of the most supported list received the fewest votes of all the candidates of the two majorities. The system makes it difficult for minority parties to elect candidates: in Case 4, candidate 3A receives the most votes, but under the binomial system, candidates 1A and 2A will be elected. As can be seen, the binomial system acts to equalize the representation of the second largest party to the point of making it roughly equal, or only slightly smaller, than that of the party winning at least a plurality. Furthermore, it acts to exclude any minority from the process, in practice generating a locked two-party, or two-bloc, system in which it is exceedingly difficult for one of the blocs to get an upper hand on the other. The table below posits the electoral results of the 2005 lower chamber parliamentary elections with three different voting systems.


Rationale

The binomial system, proponents argue, acts to stabilize the political situation by making it almost impossible for a single political bloc or coalition to make important choices in a one-sided manner.Carey, John M.:
Las virtudes del sistema binomial
, en ''Revista de Ciencia Política'', Vol.26 N°1 (2006), pp. 226–235.
This in turn leads to great political stability and prevents the emergence of the long-term personality-centered populist regimes that have been common throughout the history of Latin America. It has also been argued that it fosters consensus-building, debate and negotiation. Finally the point of representation is often cited in defense of the binomial system, as it provides a representation to the big minority that first-past-the-post systems don't.


Criticism

Critics of this system argue that it makes for a flawed democracy, as it does not necessarily elect the candidate who received the most votes. Furthermore, it effectively excludes the smaller political forces that are not a part of either of the two big electoral alliances.


References

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Bibliography

* Siavelis, Peter M.
La lógica oculta de la selección de candidatos en las elecciones parlamentarias chilenas
, en ''Estudios Públicos'', No.98 (2005), pp. 189-225. * Von Baer, Ena:
Sistema Binomial: Consensos y disensos
en ''Reforma al Sistema Binomial chileno'' Semi-proportional electoral systems Politics of Chile Polish inventions