Voting: The big problems with a “Majority Rules” system.

Recently, school started, and we had to vote for the name of our class pet(which is a venus flytrap). These were the names up for voting:

  • Mochi
  • Jaws
  • Venus
  • Trapper
  • Gardenia
  • Furious Destroyer
  • Miri
  • Cilan

The voting system we were using was a system called First Past The Post, or Majority Rules. Just like the name describes, majority rules. There is a problem with that. For example, imagine these were the results of the election:

  • Mochi = 12%
  • Jaws = 13%
  • Venus = 13%
  • Trapper = 12%
  • Gardenia = 14%
  • Furious Destroyer = 13%
  • Miri = 12%
  • Cilan = 11%

Under First Past The Post, Gardenia would have won, since it has the most votes of any other name. However, it only beat the biggest loser, Cilan, by 3%, which in a class of 24 kids is basically nothing. in fact, 86% of the class voted against Gardenia, so that is very un-representative.

Fortunately, there is a better voting system. Single Transferable Vote, or STV,

STV can be used to select any number of candidates for one district. In this case we only need one, so to win, a candidate requires 100% of the vote. Let’s see how that works..

On election day,  voters do not write one candidate on their ballot. Instead, they rank all of the candidates from favorite to least favorite.  This is how the same election will go in STV:

  • Mochi = 12%
  • Jaws = 13%
  • Venus = 13%
  • Trapper = 12%
  • Gardenia = 14%
  • Furious Destroyer = 13%
  • Miri = 12%
  • Cilan = 11%

As you can see, no one has 100% of the vote yet. So, in each round, eliminate the biggest loser. In this case, the biggest loser is Cilan. Let’s say that the Cilan voters listed Gardenia as their second choice. Now, the results look more like this:

  • Mochi = 12%
  • Jaws = 13%
  • Venus = 13%
  • Trapper = 12%
  • Gardenia = 25%
  • Furious Destroyer = 13%
  • Miri = 12%

Still, no one has 100%. So, we eliminate the next biggest loser.

In this case, it’s a tie between Mochi, Trapper, and Miri. Suppose Mochi and Miri voters both listed each other as their second choice. Both of them are out, so we do the third choices, which for both voters is Venus. And let’s say Trapper voters split between Jaws and Furious Destroyer as their second choice. We will assume that it’s a 50-50 split, so now the results look like this:

  • Jaws = 19%
  • Venus = 37%
  • Gardenia = 25%
  • Furious Destroyer = 19%

The next biggest losers are Jaws and Furious Destroyer, so we eliminate them. Let’s say all of the voters on Jaws or Furious Destroyer listed Venus as their second/third choice. So those votes go to Venus, and the results look like this:

  • Venus = 75%
  • Gardenia = 25%

There are only two names left, and Venus obviously has the majority. So Venus wins.

The best part about this method of voting is that everyone feels represented. Mochi and Miri voters chose Venus as their second choice. Jaws voters chose Venus second, and so did Furious Destroyer voters. Trapper voters chose Venus as their third choice. last but not least, Gardenia and Cilan voters all chose Venus as their third choice.

Another good thing about STV is that it works well when multiple candidates can be chosen. You just divide the number of people you want to choose by 100.

Imagine that the USA decides to send three representatives from the state of California, and there are five people running.

  • Bob
  • Jim
  • Sally
  • Darth Vader
  • Mike

When people vote, the election goes something like this:

  • Bob = 10%
  • Jim = 10%
  • Sally = 10%
  • Darth Vader = 60% – Winner
  • Mike = 10%

In First Past The Post, Darth Vader would have won the first seat, but everyone else is tied, and there are still two seats left.

However, under STV, a candidate needs 100/number of winners to win. Darth Vader has 60 percent of the vote, and he was the only one to cross the 33% percent needed to win, so we take his extra votes and redistribute them.

Suppose every one who selected Darth Vader chose a different candidate as their second choice. If 3/8th of Vader voters chose Bob, 1/4 Jim, 1/4 Sally, and 1/8 Mike, then the results look like this:

  • Bob = 32.5%
  • Jim = 25%
  • Sally = 25%
  • Darth Vader = 33% – Winner
  • Mike = 17.5%

Then, the election continues, with votes being transferred through all the candidates.

And that, readers, is Single Transferable Vote.

Please tell your teacher about this the next time you vote for the movie you are watching in class.

For a program which calculates the result of a STV election with one winner(AKA an alternative vote election),  click here

One thought on “Voting: The big problems with a “Majority Rules” system.”

  1. Great article Aryan…STV makes so much sense !! For “Majority” to rule, majority should be decided by STV 🙂

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