Gerrymandering is an issue that gets a lot of attention in the US, but what exactly is it, how does it influence the result of elections, and is it happening in Australia?

Gerrymandering is a process by which the borders of electorates are manipulated to give an unfair advantage to a particular party. To illustrate how such manipulation can be accomplished, imagine a small town with nine voting residents. Six of the residents support the red party, and the other three support the green party.

The hypothetical small town, with roof colours representing party support.
The hypothetical small town, with roof colours representing party support.

In systems such as the US Congress and Australian House of Representatives, MPs are elected on an electorate basis. Electorates divide a nation into continuous regions of land, each with roughly equal population. A candidate needs a majority of votes in their electorate to become an MP. For our hypothetical situation, let’s imagine the body responsible for drawing the borders between electorates decides that each electorate should consist of three voters. Thus we need to divide our town into three electorates. There are a few ways we can do this.

The hypothetical small town, divided into column electorates.
The hypothetical small town, divided into column electorates.
The hypothetical small town, divided into row electorates.
The hypothetical small town, divided into row electorates.

If we carve our town into electorates based on columns, we see that the two outer columns will be won by the red party, and the inner column will be won by the green party. This seems fair, since two thirds of the town voted for the red party, and the remaining third voted for the green party. But, if we divide our town along the rows, all three of the seats will be won by the red party, since they will have two thirds of the votes in each electorate. This means that despite one third of the town voting for the green party, the green party supporters will have nobody to represent them in the town’s parliament.

Gerrymandering is often an issue in the USA. North Carolina is particularly notable for this. Gerrymandering is such a big issue in the US because in most US states, electorate borders are controlled by state legislature. This means that whoever holds majority in that state’s government is essentially free to draw electorate boundaries where they please. Some states however require bi-partisan support for changes to electorate boundaries, or do so via a non-partisan commission. In Australia, the Australian Electoral Commission controls electorate boundaries nationwide, and is considered to be an impartial authority. Thus gerrymandering is seldom thought to be an issue in Australian elections.