Gerrymandering Math

We’ve all heard the word.


I doubt many of us know what it means let alone how it works.

Gerrymandering involves the dividing of a state, county, etc. into election districts. When dividing these districts, certain parties that want to sway elections will divide the counties in a way that gives their political party a majority in many districts while making sure their opposition has a majority in as few districts as possible. 

Although it sounds unfair, this is possible and is done in our current voting system. The math behind it makes it clear that this makes for an unfair political system. Take North Carolina for example.
diagram of North Carolina’s state election districts.

Above you can see a bunch of squiggly colorful states. This seems innocent and almost fun, but what you’re actually looking at is a corrupt voting system. In its most recent congressional election, North Carolina’s congressional delegation remained as a 10-3 Republican majority, despite half of the total votes being cast by Democrats. How does this happen? Gerrymandering of election districts to favor the Republican Party is how.

Patrick Honner, a Contributing Columnist for Quanta Magazine, explains the math of Gerrymandering.

“Start by imagining a state with 200 voters, of whom 100 are loyal to party A and 100 to party B. Let’s suppose the state needs to elect four representatives and so must create four districts of equal electoral size.

Imagine that you have the power to assign voters to any district you wish. If you favor party A, you might distribute the 100 A voters and 100 B voters into the four districts like this:

D1 D2 D3 D4
A 30 30 30 10
B 20 20 20 40

With districts constructed in this way, party A wins three of the four elections. Of course, if you prefer party B, you might distribute the voters this way:

D1 D2 D3 D4
A 20 20 20 40
B 30 30 30 10

Here, the results are reversed, and party B wins three of the four elections.

Notice that in both scenarios the same number of voters with the same preferences are voting in the same number of elections. Changing only the distribution of voters among the districts dramatically alters the results. The ability to determine voting districts confers a lot of power, and attending to some simple math is all that’s needed to create an electoral edge.”

Although you cannot simply divide your voters into districts based on their preference, this is the basic idea Gerrymandering. Those creating district lines can track voting data from different regions of a state to see what the general preference of the area is. They then can draw lines to distribute voters similarly to what is done above.  The result is a diagram similar to North Carolina.

Looking at the math, Gerrymandering essentially “waste” the votes of those in a party that is ‘corraled’ – if you will – into fewer districts to suppress their vote.

The process of Gerrymandering causes there to be one or two districts who all prefer party A, and the rest have a majority of party B. This would make for a certain party to have a majority over whatever they are being voted into. What we can learn from Gerrymandering is this. Our voting system is so flawed that we can draw lines on a map and suppress thousands of votes.

-and we can do this legally.

2 Replies to “Gerrymandering Math”

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    Yet another aspect of voting I not know about. This class has really opened my eyes and made me look at the world differently. This idea of shaping the voting area to favor one specific party is outrageous. However, it is vary interesting how it works and that it is even allowed. An article by Washington Post explains were the term Gerrymandering comes from. A 19th century Massachusetts governor, Elbridge Gerry, created a grid that favored a specific party in 1810. The shape of that boarder for one of the groups almost depicts a salamander. Thus the term Gerrymander was created.

  2. I’ve never heard the term “gerrymandering” before, but I was familiar with the concept of it. I completely agree with you that this system is flawed and unfair. It can cause minorities to have less of a say in the areas in which they vote for an official. Gerrymandering often disproportionately represents one class/political leaning to ensure a certain candidate or party will win the election, which is just corrupt and I am shocked that this system is still being used.

    I found a pretty recent example which showcases Michigan’s skewed districts.
    “We found Michigan’s legislative and congressional districts exhibit extreme values with the efficiency gap, which is suggestive of gerrymandering. In the original 2012 analysis by the academics who devised this measure, Michigan was one of seven states where congressional districts exceeded the proposed acceptable level, and one of 13 states where state house districts exceeded the recommended maximum efficiency gap. Michigan was one of only four states (along with Florida, North Carolina, and Ohio) where both legislative and congressional maps were graded as extreme.”

    I found this paragraph in an online article, published by Eric Lupher last summer. You can read more about it here:

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