Duverger's Law

Duverger’s Law

The purpose of this blog is to explore the relationship between the electoral system and the number of relevant political parties in a state.  More specifically I will discuss whether Duverger’s law (and Cox’s modification of this law), which states that “the effective number of parties in any electoral district is a function of the electoral rules: SMDP rules produce two effective parties, while proportional representation rules allow for more,” is true.[i]  For this post I have chosen to research the electoral system of Peru. 

To start, some background information about Peru’s government will be necessary.  Peru utilizes a proportional representation system, meaning that the strength of political parties in congress is proportional (more or less) to their strength in the electorate.[ii]  Since this is the case, I will be looking to see if there is a large amount of effective number of parties in the country, not just two. 

Delving deeper, the specific type of PR (proportional representation) system of Peru uses a closed (nonpreferential) party list structure.[iii]  Thus, parties create and submit a list of candidates from their party, and voters vote for political parties, not for specific candidates. 

The country is divided up into 25 administrative regions, and directly elects the 130 seats of their legislative body, Congreso de la República.[iv] Based on what I could find, it appears that the district magnitude of each region is around 5.2.  I took the total number of seats in the congress and divided it by the number of constituencies assuming that each district elected roughly the same number of seats. 

One final piece of background information to consider that could contribute to the number of effective parties in Peru is its threshold, or the rules for how many votes you need to retain you status as a legitimate party.  Not a lot of information could be found on this subject.  However one article on political party aid written in 2004 did say that “The main Peruvian political parties… successfully pushed for the enactment of a new political party law….It raises the petition signature threshold for the registration of parties and requires parties to have offices in many parts of the country.”[v]   

Based on the prior background information on the electoral rules of Peru, it is clear that it uses a PR system.  Now to see if this coincides with Duverger’s law that states as a result of the PR system used there should be more than two effective parties competing for power.    

In the latest elections in 2011, there were no less than 13 parties or coalition of parties facing off to win seats in the congress.[vi]  Several of Peru’s parties who won seats were actually coalitions of parties.  For example the party Gana Peru who won 25.3% of the votes and 47 of the 130 seats is made up Partido Nacionalista Peruano, Partido Socialista, and others.

Although several parties participated in the elections, it remains to be seen how many effective parties are operating in congress.  To do this, I used the formula discussed in our last lecture:

Political Party	Percentage Votes	Seats Won	Percentage Seats	Porportion Squared
Gana Peru	25.30%	47	0.361538462	0.130710059
Fuerza	23%	37	0.284615385	0.081005917
PP	14.80%	21	0.161538462	0.026094675
Alliance for great change	14.40%	12	0.092307692	0.00852071
National solidarity	10.20%	9	0.069230769	0.004792899
Peruvian aprista party	6.40%	4	0.030769231	0.000946746
Sum				0.252071006
1/sum (# of effective parties)				3.96713615

Based on this formula, there are 4 effective parties operating in Peru’s congress. 

To conclude, no two parties dominate the political stage, and there are several operating political parties in the country, and based on the formula there are four effective parties in Congreso de la Rebública.  Therefore, In considering the political parties and the electoral system of Peru, Duverger’s law holds true. 

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[i] Assignment Details: Duverger’s Law. Learning Suite. <https://learningsuite.byu.edu/student,home.0>

[ii] Shively, W. P. "Chapter 10: Elections." Power & Choice An Introduction to Political Science. New York: McGraw-Hill, 2012. 231. Print.

[iii] "IPU PARLINE Database: PERU (Congreso De La República), Electoral System." IPU PARLINE Database: PERU (Congreso De La República), Electoral System. Inter-Parliamentary Union, 2012. Web. 02 Nov. 2012. <http://www.ipu.org/parline-e/reports/2251_B.htm>

[iv] "Central Intelligence Agency." CIA. CIA, Nov. 2012. Web. 02 Nov. 2012. <https://www.cia.gov/library/publications/the-world-factbook/geos/pe.html>

[v] Carothers, Thomas. Political Party Aid. Rep. Carnegie Endowment for International Peace, n.d. Web. 1 Nov. 2012.

[vi] "Elections in Peru." Wikipedia. Wikimedia Foundation, 25 Oct. 2012. Web. 02 Nov. 2012. <http://en.wikipedia.org/wiki/Elections_in_Peru>.