Proportional Represenation versus Plurality

In IS210 we will discuss the relative merits of the two most frequently instituted electoral systems–proportional representation and plurality (also called majority or “first-past-the-post” electoral systems.

In advance, here is a chart that I’ve created, which shows the electoral results (in terms of number of seats won in the House of Commons) of the 2011 Canadian Federal election. The bottom of the chart contains the actual number of seats won, while the top lists the hypothetical number of seats each party would have won if Canada’s electoral system were one of proportional representation. So, Canada’s electoral system is working as it should, correct?

canada_2011_election_PR

John Cleese on Proportional Representation

There are generally two types of electoral system in use around the world–first-past-the-post (single-member district) and proporational representation (multi-member district).

As John Cleese explains in this public service announcement, the choice of which electoral system to implement in a democracy can have a dramatic impact on party politics and on the political system in general.  The idea behind proportional representation is that the composition of the legislative body is directly representative of the political opinions in the electorate.  So if, for example, 3% of the electorate votes for the Polish Beer-Lovers’ Party (PPPP–Polska Partia Przyjaciół Piwa), as happened in the Polish parliamentary elections of 1991, then that party will have 3% of the representatives in the legislative body (which it did).

In first-past-the-post systems, such as the USA, Canada, and the UK, the electorate is divided up into single-member-districts, from which a single representative is elected to represent that seat in the parliament.  The winner does not have to win a majority of the vote, only a plurality.  Thus, if there are 4 contenders for a particular seat, and three of them each garners 20% of the vote, the fourth candidate, with 40% of the vote, wins the seat, representing that district in parliament.  The rest of the votes (the 60% going to non-winning parties) is “wasted” as it is not used to determine representation in parliament.  These are the basics, but upon these foundations one can build a myriad of different types of systems, such as the “double-vote” system in Germany.