Redistricting / Gerrymandering 101

A Demonstration using Geometry

It may be hard for some to visualize how the choice of district can affect representation, so I built a clear demonstration using simple geometry.

Full size image (with text) here.

Here are three 'populations'. These populations are split 50% red and 50% blue. The dashed lines divide them into 'districts'.

The first population (1) has an offset center. The second (2) and third (3) do not. The areas of the color in each population are identical, even if the blue circle appears to be larger than the red square.

How we choose the dashed lines has an interesting effect on the color of the boxes: the color with the greatest area in the district sets the color of the smaller box, or 'representative'. The representatives get to vote on policy for the entire population.

In the second set of representatives, blue is disproportionately represented, if slightly. In the third set, red is firmly and unfairly in control of the votes. This degree of skew is achieved using a simple grid over a square and circle. Were the shapes more complex, the skew could be much greater.

Depending on who is choosing the district lines and what their agenda is, the number of representatives can be skewed disproportionately respective to the population. This is why the US House of Representatives currently has 232 red votes and 199 blue votes even though in the 2012 Presidential Election there were 66 million blue votes, and only 61 million red votes. This has very little to do with the 'will of the people'.

We call the process of subverting democracy through redistricting 'gerrymandering'.

Now you know how it works. How unfairly districted is your state?

For the curious: the square has an edge length of 2", the circle a radius of 0.798". Had the circle in the first population been exactly centered, every square would've also been split 50/50 and I'm not in Florida, hence the offset. The image was built using Omnigraffle Pro. The font is 'Anonymous Pro'.