Click the buttons to spin the wheel and see how changes in constituency boundaries can dramatically effect the outcome of an election. The black lines represent our constituency boundaries, whilst the coloured dots represent the voters.
As you can see, although the voters don't move or change their minds about the party that they are going to vote for, the winners change as the constituency boundaries change. Simply by redrawing the boundaries we can go from Labour having won 4 seats and the Conservatives 1, to the Conservatives coming out as winners by 3 seats to Labour's 2.
So why does this happen?
Boundaries between constituencies can often just manage to give a party a slim majority where a different arrangement would not. People who vote for a party which narrowly loses will find that their vote is wasted. This doesn't just happen as a result of deliberate tampering, but can also occur when the boundaries are drawn up in an impartial way.
So what's the solution?
The solution is to switch to a voting system with fewer wasted votes based on multi-member constituencies (preferably STV).
I've also put together a very basic PowerPoint version of the wheel, which I hope someone will find useful.
Fairvote have also produced a version of the wheel based on a two party system.
Credit must be given to the Proportional Representation Society of Australia who originally came up with the idea of a Gerrymander Wheel.