Thursday, November 1, 2012

Duverger's Law


        Duverger’s Law claims that the effective or influential number of parties in any electoral district is a function of the electoral rules. Electoral systems can be broadly divided into two categories: single-member-district plurality systems (SMDP) and proportional representation (PR) systems. SMDP systems occur where a state is divided into districts with roughly equal populations, and a single candidate is elected from each district by a plurality (rather than a majority) of votes (Samuels). PR electoral systems occur under a system where "political parties representation in the legislative body is roughly proportional to their strength in the electorate” (Samuels). According to Duverger’s Law, SMDP systems produce two effective parties, while PR systems produce more. To test this law, we will consider the electoral rules for the United Kingdom, specifically the lower chamber of Parliaments: the House of Commons, which is classified as a SMDP system.
            Electoral systems are governed by certain rules that determine which parties or candidates win office as a result of any kind of a vote. These electoral rules include the district magnitude, the formula used to allocate the seats according to the vote, whether the system is a hybrid, the list structure, and if there are any thresholds. The district magnitude is how many seats are allocated to each electoral district. In the United Kingdom, there are 650 electoral districts, with a single member elected from each district (IPU Parline). So the district magnitude (m)= 1.
            The formula used to determine who wins the seat in the House of Commons is a plurality, or “first-past-the-post” rule (IPU Parline). Basically whichever candidate receives the most votes, wins. As opposed to a PR formula where the seats which be allocated proportionally to the number of votes a party receives. The United Kingdom is definitely not a hybrid system, like Germany. It doesn’t combine any elements of SMDP and PR system together, it completely a SMDP system regarding to the election of members to the House of Commons.
            The list structure is whether people vote from a list of parties and just vote for the candidates directly. In closed/nonpreferential list structures, people vote for a party and the party leaders decide which candidates are put in office. In an open/preferential list structure, voters decide which candidates are put in office directly. In the United Kingdom, people vote for the candidates directly, not the parties, so it is an open list structure (UK Parliament).  There are not any thresholds in the UK, where parties have to get a minimum percentage of votes to have them count or to retain your party registration. In the UK, you can run as an independent or with a party and the votes will still count.
            Given these electoral rules, the United Kingdom is definitely a single-member-district-plurality system. So according to Duverger’s Law, the United Kingdom should have two effective parties. A formula can be used to determine the effective number of parties: Neff= 1/Σ(p2), where p= proportion of seats won by each party. In the 2010 election for the House of Commons, the Conservative Party won 47% of the seats, the Labour Party won 39%, and the Liberal Democrat Party won 8% of the seats, all of the other 47+ parties or independent candidates were negligible (Wikipedia Election World). Using this formula, it can be determined that the United Kingdom has 2.63 effective parties. So basically the UK has two effective parties, the Conservative and Labour Parties, with a third somewhat influential party (the Liberal Democrats). Using the United Kingdom as a test case, it turns out that the Duverger’s Law is correct; SMDP electoral systems tend to produce two effective parties.


Sources:
"United Kingdom- House of Commons." IPU Parline. Inter-Parliamentary Union, n.d. Web. 1 Nov. 2012.

"General Elections." - UK Parliament. N.p., n.d. Web. 01 Nov. 2012. <http://www.parliament.uk/about/how/elections-and-voting/general/>.

"Elections in the United Kingdom." Wikipedia. Wikimedia Foundation, 27 Oct. 2012. Web. 02 Nov. 2012. <http://en.wikipedia.org/wiki/Elections_in_the_United_Kingdom>.

Samuels, David J. Comparative Politics. N.p.: Pearson, 2013. Print.

1 comment:

  1. I think this was well written, so good job. You explained your thesis and then clearly backed that up. I had no idea that the United Kingdom was an SMDP so thank you for that information.

    ReplyDelete