There are many different systems for elections around the world. Proportional Representation is a method that maximises the effectiveness of votes cast in elections leading to the election of parliaments which most closely reflects the wishes of the electorate at large.
Parliamentarians in the South Australian House of Assembly, the House of Parliament that decides who the Government will be, are elected from single member electorates. To be elected in a single member electorate a candidate needs just over 50% of the vote. This means that almost 50% of votes in that electorate are not used to elect anyone - often described as wasted votes.
Generally speaking, if you voted Liberal in an electorate where a Labor candidate won or alternatively if you voted Labor in an electorate where a Liberal candidate won then your vote was not effective. This is not to say that you do not have the right to vote for your choice, but the system of single member electorates that we have fails to maximise the effectiveness of the votes cast in elections.
Electing a Parliament from single member electorates not only reduces the number of effective votes but also can lead to distortions in outcomes of elections. The gerrymander wheel illustrates how drawing the boundaries for single member electorates differently can result in substantially different results in any given election.
The Center for Voting and Democracy (USA-based; includes legislation, list of countries using PR and other info) has an online Javascript version of the PRSA "Gerrymander Wheel" which allows you to play Redistribution Roulette to show how single member electorates can lead to almost arbitrary electoral outcomes, depending on electorate boundaries.
So how do we fix this? If instead of having individual electorates we merge two electorates together this would mean that we would have half as many electorates will the same number of parliamentarians. In this case to be elected each Member of Parliament would need just over 33% of the vote. With two MPs in each electorate the minimum votes used is just over 66% (33% +33%) and hence the maximum potential for wasted votes is just under 33%.
If we take this further, and have five MPs per electorate the potential for wasted votes is only 16.5%.
The South Australian Legislative Council (the Upper House) is elected through a system of proportional representation. While the system used in the Legislative Council is not perfect, it does have the benefit of being a more representative House of Parliament.
At each election there are 11 Members of the Legislative Council elected from one electorate that encompasses the entire state. In this case the maximum potential for wasted votes is 8.3% of the vote. In this case the system of PR ensures that at least 92.7% of the vote actually counts, meaning that most voters have someone of their choice voted into the Legislative Council.
