Good afternoon! Gerrymandering was in the news this week, when the Supreme Court declared that gerrymandering for political purposes is totally fine. So this seems a good moment to give the briefest of introductions to gerrymandering. The idea behind it is that districts can be divided up in such a way as to maximize the chances of one party winning. There are sometimes some rules, like that regions have to follow natural boundaries, but the name itself comes from an 1812 cartoon (probably by Elkanah Tisdale) making fun of a redistricting in Massachusetts that led to a salamander-like voting district. The bill allowing the district had been signed by Governor Elbridge Gerry
Gerrymandered districts…
Good afternoon! Gerrymandering was in the news this week, when the Supreme Court declared that gerrymandering for political purposes is totally fine. So this seems a good moment to give the briefest of introductions to gerrymandering. The idea behind it is that districts can be divided up in such a way as to maximize the chances of one party winning. There are sometimes some rules, like that regions have to follow natural boundaries, but the name itself comes from an 1812 cartoon (probably by Elkanah Tisdale) making fun of a redistricting in Massachusetts that led to a salamander-like voting district. The bill allowing the district had been signed by Governor Elbridge Gerry
Gerrymandered districts have a reputation for having strange shapes, as in the cartoon above, but even with more regular shapes there can be a lot of maneuvering that can be done. For example, suppose you have this area and you want to divide it into 5 districts, with the idea that each district is connected, but you happen to know that people living in the gold areas will reliably vote Gold and people living in the Purple areas will reliably vote Purple.
You could split it into districts horizontally, ending up with 2 Gold reps and 3 Purple reps. This is called packing, because all the districts of one color are packed together, although it happens equally between the two parties.
But you could instead split it into vertical districts, ending up with 5 Purple reps. This is called cracking, because the yellow districts are split up so that they don’t end up with any power.
It’s also possible to split it up so that there are 3 Gold reps. This is also cracking.
From a mathematical perspective it can be difficult to determine if a district is gerrymandered for a particular purpose, unless the people announce it. But if people did want to avoid gerrymandering for any purpose, that is something that math can help with. There are articles like “How Math Has Changed the Shape of Gerrymandering” by Mike Orcutt from Quanta Magazine, and sites like the Institute for Mathematics and Democracy, as well as “The (very) tricky math of detecting gerrymandering in election districts” by Keith Devlin with Ellen Veomett
This will be the last Monday (sometime) Math until late January. I hope that everyone has a peaceful end of 2025!
Tags: Elections, gerrymandering, History, news, politics
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