How is the ranking choice better

What are the arguments against voting by election?

This problem can be solved by a system known as ranked voting, also known as instant voting

First of all, there are several voting systems based on the ranking of your selections. The system you are describing is just an example, and it's a pretty bad one. It's frustrating, therefore, that people are calling it the "ranking poll" as if it were that only one Ranking system.

This system is more precisely referred to as "instant runoff voting". (Although taken literally, there are other systems that use instant rounds of drain, but "IRV" always means that particular system.)

Second, it has a number of problems:

IRV has a spoiler effect

You said:

It removes the concern of third party candidates appearing as spoilers.

However, it doesn't. It actually leads to two-party rule in every country where it is adopted.

It is true that it is safe, honest for one Marginal candidates (Yellow) to vote, as these will be eliminated immediately and your second choice will go to a main candidate (Green). So IRV is better than plurality in this case (where red would win even though a majority is against red):

However, as the third-party candidate becomes more competitive (which is the whole point of adopting an alternate voting system), voting for him honestly removes votes from your second choice, which is eliminated first, and then from your least-loved candidate in win the next round. If the third didn't run, your more preferred candidate would have won, so the third acts as a spoiler, and indeed the effect is worse than in the plural (red bar extends further to the right):

Video illustration of this effect:


Favorite treason in plurality and immediate runoff

These effects were graphically modeled on one-dimensional and two-dimensional political spaces and generate bizarre profit regions in which the population, who on moves a candidate, makes them lose and vice versa. In this example, if the population's opinion shifts to the right, if support for red is reduced and support for yellow is increased, then red would win instead of green !:

In two dimensions we can see how IRV gives the choice to green, even if the population is focused precisely on the yellow candidate. There is also a bizarre yellow island that is not near the yellow candidate and is not present in any of the other voting systems depicted.

The consent vote or the Condorcet ranking both have meaningful results, with the candidate closest to the population center winning:

Animated 2D comparison of different systems:


Yee animations 0.8

IRV rules out moderates

Similar to above, if there are two more extreme partisan candidates and one moderate / compromise candidate in the middle, the compromise candidate will be eliminated prematurely (because he is not the first choice) even though he is the best representative of the population as a whole, and instead becomes a more partisan candidate elected. This is known as the "center squeeze effect".

This essentially happened in the 2009 elections in Burlington Vermont, which resulted in the repeal of the IRV. Montroll was "centrist" compared to the other main candidates, but was eliminated in the 4th round and a more extreme candidate won, although Montroll had a higher approval rating than the winner.

Here are the ideal winning regions for 14 candidates, with everyone winning when the population center is near them:

Here's what happens in IRV. All candidates near the center are eliminated, and only the more extreme fringe candidates can win:

These two effects lead to political polarization and two-party rule. You can see IRV skew the Australian house in favor of the two main parties, although 1/4 to 1/3 of the population would prefer third parties (while STV results in a more proportional Senate):

IRV is not a Condorcet system

In the Burlington election, Montroll was also the Condorcet winner, meaning he would have won head-to-head against any other candidate. The general preferences of the population were clear: Montroll> Kiss> Wright> Smith> Simpson. However, IRV is not a Condorcet system. it eliminated Montroll and instead chose the population's second favorite kiss.

If your system doesn't have the most popular Candidates (the "Utilitarian Winner") elects, it should at least be the most preferred Elect candidates (the "Condorcet Winner"). IRV guarantees neither.

IRV enables majority tyranny

Here is a (made up) example:

  • Candidate A is loved by 55% of the population and hated by 45% of the population (55% overall approval rate)
  • Candidate B is liked by everyone (85% overall approval rate)

Under IRV, the polarizing candidate A would win because he is preferred by a majority, although the population as a whole would be much happier if candidate B won the election.

"Utilitarian" voting systems such as Score / Approval select the candidate with the higher approval rate, which is viewed by proponents of these systems as a better result.

Another view is that Candidate A is a great representative of the half of the population, while candidate B is a good representative of the entire Population is.

Majority voting systems are not as comprehensive, which leads to controversial politics, inefficiency and even civil wars.

Election 2016

And if the Republican primaries had voted a post-election vote, Trump would not have won the nomination as a majority of voters were against him. It's just that the anti-Trump vote was split.

There isn't a lot of good data on this, but it's likely that IRV would still have voted Trump:

Score or Condorcet voting would probably have chosen Sanders or Kasich, as they had the highest approval ratings:

Keshav Srinivasan

Well, I think the point of voting is majority rule, and then you should use other mechanisms like checks and balances and the like to deal with the fact that there is a minority who disagree with the majority. Anyway, do you know of a voting system that improves the IRV in other ways, but still A wins against B in the example you gave at the end?

Endolite

@ KeshavSrinivasan I'm just curious how you came to this conclusion. Isn't it the purpose of elections to choose the candidate who best embodies the will of the people? Anyway, Condorcet systems are majority too, so you might like these. Schulze is the only one I've talked about so I'm assuming he is in some ways superior to the others, even though I don't know the details.

Endolite

@KeshavSrinivasan Score Runoff Voting uses First Round Score to select the two candidates with the highest approval ratings (instead of the party primaries) and then competes in an instant runoff that gets the majority of the votes. So it is majority in a sense, but only after first eliminating the extremely polarizing candidates. Simulations say it resists strategic coordination better than pure score.

Endolite

@blip There are many ranked voting systems in existence, but the term "ranked voting" is commonly used to refer to this system, particularly in the United States. Literally, I think there are other voting systems that use "instant outflow" rounds, but likewise the term "IRV" refers almost exclusively to that system. I'll edit to be more specific. Center squeeze does not occur in all ranking systems. Condorcet systems like Schulze would have chosen Montroll, for example.

Indigochild

Where did you get these numbers from (or how did you make them)? I love her.