I think people often dismiss systems like STV/IRV by essentially saying "Arrow's theorem implies you can still vote tactically, so it's just as bad". But there's a big difference: in STV it's much harder to figure out how to vote tactically.
In First Past The Post systems, tactical voting is blindingly obvious: if there are two candidates you like, but you don't think that your favourite has enough popularity to win outright, then you should vote for the other one, to avoid splitting the vote. This is easy to understand, and it's also easy to detect circumstances where it would be beneficial for you to vote other than your preferences.
OTOH, even though there are times where you can vote tactically in STV, they're harder to understand, and crucially, it's much harder to recognise such opportunities: you need a lot more information.
This means that, in general, STV would cut down on tactical voting a great deal, simply because it makes it harder.
This. In FPTP, tactical voting will have a major influence on the results, since it's so obvious and thus lots of people will end up doing it. In STV, most people won't even realize that the opportunity for tactical voting exists, so the amount of people doing it will be much smaller.
in general, STV would cut down on tactical voting a great deal, simply because it makes it harder
Possible counterexample:
In the USA, tactical voting for President is usually completely impossible, due to the electoral college system. Your vote only affects the election outcome if the election as a whole is a toss-up and if your home state is in play. But for a Texan like me, that will never occur, not even relative to the one-in-a-million odds you'd normally expect from a national election. If the Democratic candidate stands any chance of winning here, they'll be winning the rest of the country in a landslide. Likewise for a Californian: any situation in which the Republican might win California is a situation where they've surely already won nearly everywhere else. Likewise for most of the country; only a handful of states, known well in advance, are "swing states" in a given election.
Yet, other than a few weirdos like me, does anyone use this freedom-means-nothing-left-to-lose situation to vote for a third party and thereby at least influence news results? Granted that most people usually prefer the two leading parties' candidates, but I haven't seen any statis...
I imagine that if polls showed that we were in a situation where strategic voting might be useful for people with certain preferences, the news media would report on it and people would learn about it.
I can see the headline now: "Mathematician says that if your preferences are 'A > B > C', you should vote 'B > A > C' in November!"
Such situations could be recognized by poll questions like "What is your preference ordering over these 3 candidates?" Candidate B's campaign would have a large incentive to publicize this information.
The 60,000 Florida citizens who voted Green in 2000 didn't result in Nader for President (they did result in a nadir for the presidency, but that's different)
The parenthetical statement, while mildly funny, is unnecessarily political and detracts from the substance of your post.
Upvoting for capturing the remark for those of us who didn't catch it before it was edited out. Yvain has the best puns.
I vote for range voting. It has the lowest Bayesian regret (best expected social utility). It's also extremely simple. Though it's not exactly the most unbiased source, rangevoting.org has lots of information about range voting in comparison to other methods.
The 60,000 Florida citizens who voted Green in 2000 didn't result in Nader for President (they did result in a nadir for the presidency, but that's different) . However, they did make Gore lose to Bush by a mere 500 votes.
The same could be said for the 562 voters for James Harris of the Socialist Workers Party.
I've used this as an example of the problem with 'Highlander thinking', or the claim that there can be only one cause. Seems to me that any number of changes to the timeline would hand Gore the Presidency.
It's even harder to see when you ought to strategically vote in Condorcet systems than under STV. The strategic voting style you'd aim for in Condorcet is to 'bury' a second-favorite candidate.
Case: A Blue. Thinks the Reds have some serious problems, but those problems are nowhere near as bad as the White party.
The honest vote here is to vote Blue - Red - White. The strategic vote is Blue - White - Red.
But that is a very risky move. It only helps if this vote-bury helps the White party beat the Red by direct preference, AND the Red beat the Blue, AND the Blue beat the White party by direct preference, - so we just helped make a cycle - AND the cycle-resolution system, whatever that is, ends up favoring the Blues.
If you get the first and the second but not both of the other two... congratulations, you just elected the White party (or you made a cycle, and though the Red won, you made the Whites gain reputation and power relative to where they'd be being eliminated).
Unless you can know a great deal about the ballots that have been cast, this is far more likely to backfire and get you something you really don't want (White winning) than to get you something you want (Blue winning).
I'm moderately in favor of randomly sampling members of legislative bodies from the represented population. The U.S. would only need a thousand citizens in Congress to have the national opinions and beliefs represented with the same accuracy as a Gallup poll. The period from November to January could just be a crash course in parliamentary procedure and the legal system.
Stalin once (supposedly) said that “He who casts the votes determines nothing; he who counts the votes determines everything “
The original Russian and a better translation together with some background on the Stalin quote can be found here. Of course, this is not from an official record, and so could have been made up or mis-remembered.
You confuse AV ('Instant Runoff') with STV (AV in multi-member constituencies). The incentives for STV and AV are very different.
"The Liberal Democrats, who were perpetually stuck in the same third-place situation as Nader in the States, supported a change to a form of instant runoff voting which would have made voting Lib Dem a much more palatable option; the two major parties opposed it probably for exactly that reason."
Actually, most studies showed that if anything the support for the Lib Dems would drop slightly rather than rise under AV (the...
My morning coffee hasn't kicked in... I wonder what the significance is that no voting system can be "perfect". Is it a fluke of math, or does it say something about the coherence of our value systems as they pertain to electoral systems?
I should also express my view that a plurality voting system that allows only two parties to thrive in practice is probably the worst of all worlds where it concerns voting systems. I believe the polarizing effects of a system that requires exactly two parties are a large component of the set of difficulties that make it so politics is the mind-killer.
Do these systems avoid the strategic voting that plagues American elections? No. For example, both Single Transferable Vote and Condorcet voting sometimes provide incentives to rank a candidate with a greater chance of winning higher than a candidate you prefer - that is, the same "vote Gore instead of Nader" dilemma you get in traditional first-past-the-post.
In the case of the Single Transferable Vote, this is simply wrong. If my preferences are Nader > Gore > Bush, I should vote that way. If neither Bush nor Gore have a majority, and N...
(one example of an unreasonable system that eliminates tactical voting is picking one ballot at random and determining the results based solely on its preferences; the precise text of the theorem rules out “nondeterministic or dictatorial” methods).
Not sure if this is covered elsewhere in the comments since it wasn't easy to search for, but is there anything actually wrong with this apart from the fact that people would feel really weird about it, and maybe be worried that the process picking the vote is unfairly weighted somehow?
It would appear that many of these problems would be circumnavigated, if voters were permitted to save their votes. In the case that none of the candidates were to my liking, I could then save up my vote for any forthcoming election. When, after a 50 years of waiting, I am finally offered a candidate of my liking, I may then have an opportunity to spend all 50 of my votes at once (great for minorities who are never offered a meaningful choice.)
A system based upon non expiring votes would likely be sufficiently unpredictable to discourage strategic voting (...
Another example for the influence of voting systems:
In Germany, the voting system was recently changed due to some very problematic edge cases. While the new voting system has its own problems (of a similar severity), a newspaper used the opportunity to compare the distribution of seats in parliament among the political parties according to the 2009 election (under the old voting system) with the distributions that would have resulted from the same voting behavior under many different voting systems.
The results of this comparison can be found here. (Use th...
I wish this post would have more gone into the issues of what you are voting for, and how the appropriateness of the voting system depends on that. Counting the votes is not an end in itself, but a reflection of actual decisions to be made, often including further votes.
For example a British MP does not have authority in his own right; he only exercises power through his vote in Parliament. Few would argue that choosing ones own MP is an end in itself; the important thing is that the voter should be able to influence the decisions of the government as a wh...
You can solve the domination problem by just picking a vote at random, and having that vote be the deciding vote. So if 49% of people vote for Bush, and 49% vote for Gore, and 2% vote for Nader, then Bush, Gore and Nader have a 49, 49 and 2% chance of winning respectively. In this system, you can always vote for your favorite candidate without worrying about how electable they are.
(one example of an unreasonable system that eliminates tactical voting is picking one ballot at random and determining the results based solely on its preferences; the precise text of the theorem rules out “nondeterministic or dictatorial” methods).
I'm a big fan of approval voting, because while it does have strategic voting concerns, the way they work is intuitive. Instant-runoff's occasional non-monotonic results seem like inviting a scandal, and Condorcet seems too opaque and to ask for too many decisions.
I think you underestimate how difficult it is to create a voting system that won't utterly baffle a large portion of the electorate. People in general aren't good about reading instructions, and they often get confused about the simplest of things. While I like both Condorcet and approval voting, I prefer approval voting for being stupidly simple. "Vote for the people you think would do a good job; the person with the most votes wins," is a very easy thing to understand, so most people will probably get it.
(Think I'm being too cynical? Try writing non-trivial instructions aimed at ordinary people. You'll see.)
Do these systems avoid the strategic voting that plagues American elections? No. For example, both Single Transferable Vote and Condorcet voting sometimes provide incentives to rank a candidate with a greater chance of winning higher than a candidate you prefer - that is, the same "vote Gore instead of Nader" dilemma you get in traditional first-past-the-post.
Depends—whether you get that dilemma with Condorcet methods depends on how exactly you handle tied ranks. If you require a full majority (>50% of votes) to declare one candidate defeats another, yo...
Here is a 30-minute Great Course starring Professor Scott P. Stevens: The science of election methods
tldw: at 28:53, he recommends Range Voting.
Stalin once (supposedly) said that “He who casts the votes determines nothing; he who counts the votes determines everything “ But he was being insufficiently cynical. He who chooses the voting system may determine just as much as the other two players.
The Art of Strategy gives some good examples of this principle: here's an adaptation of one of them. Three managers are debating whether to give a Distinguished Employee Award to a certain worker. If the worker gets the award, she must receive one of two prizes: a $50 gift certificate, or a $10,000 bonus.
One manager loves the employee and wants her to get the $10,000; if she can't get the $10,000, she should at least get a gift certificate. A second manager acknowledges her contribution but is mostly driven by cost-cutting; she'd be happiest giving her the gift certificate, but would rather refuse to recognize her entirely than lose $10,000. And the third manager dislikes her and doesn't want to recognize her at all - but she also doesn't want the company to gain a reputation for stinginess, so if she gets recognized she'd rather give her the $10,000 than be so pathetic as to give her the cheap certificate.
The managers arrange a meeting to determine the employee's fate. If the agenda tells them to vote for or against giving her an award, and then proceed to determine the prize afterwards if she wins, then things will not go well for the employee. Why not? Because the managers reason as follows: if she gets the award, Manager 1 and Manager 3 will vote for the $10,000 prize, and Manager 2 will vote for the certificate. Therefore, voting for her to get the award is practically the same as voting for her to get the $10,000 prize. That means Manager 1, who wants her to get the prize, will vote yes on the award, but Managers 2 and 3, who both prefer no award to the $10,000, will strategically vote not to give her the award. Result: she doesn't get recognized for her distinguished service.
But suppose the employee involved happens to be the secretary arranging the meeting where the vote will take place. She makes a seemingly trivial change to the agenda: the managers will vote for what the prize should be first, and then vote on whether to give it to her.
If the managers decide the appropriate prize is $10,000, then the motion to give the award will fail for exactly the same reasons it did above. But if the managers decide the certificate is appropriate, then Manager 1 and 2, who both prefer the certificate to nothing, will vote in favor of giving the award. So the three managers, thinking strategically, realize that the decision before them, which looks like “$10 grand or certificate”, is really “No award or certificate”. Since 1 and 2 both prefer the certificate to nothing, they vote that the certificate is the appropriate prize (even though Manager 1 doesn't really believe this) and the employee ends out with the gift certificate.
But if the secretary is really smart, she may set the agenda as follows: The managers first vote whether or not to give $10,000, and if that fails, they next vote whether or not to give the certificate; if both votes fail the employee gets nothing. Here the managers realize that if the first vote (for $10,000) fails, the next vote (certificate or nothing) will pass, since two managers prefer certificate to nothing as mentioned before. So the true choice in the first vote is “$10,000 versus certificate”. Since two managers (1 and 3) prefer the $10,000 to the certificate, those two start by voting to give the full $10,000, and this is what the employee gets.
So we see that all three options are possible outcomes, and that the true power rests not in the hands of any individual manager, but in the secretary who determines how the voting takes place.
Americans have a head start in understanding the pitfalls of voting systems thanks to the so-called two party system. Every four years, they face quandaries like "If leftists like me vote for Nader instead of Gore just because we like him better, are we going to end up electing Bush because we've split the leftist vote?"
Empirically, yes. The 60,000 Florida citizens who voted Green in 2000 didn't elect Nader. However, they did make Gore lose to Bush by a mere 500 votes. The last post discussed a Vickrey auction, a style of auction in which you have have no incentive to bid anything except your true value. Wouldn't it be nice if we had an electoral system with the same property: one where you should always vote for the candidate you actually support? If such a system existed, we would have ample reason to institute it and could rest assured that no modern-day Stalin was manipulating us via the choice of voting system we used.
Some countries do claim to have better systems than the simple winner-takes-all approach of the United States. My own adopted homeland of Ireland uses a system called “single transferable vote” (also called instant-runoff vote), in which voters rank the X candidates from 1 to X. If a candidate has the majority of first preference votes (or a number of first preference votes greater than the number of positions to fill divided by the number of candidates, in elections with multiple potential winners like legislative elections), then that candidate wins and any surplus votes go to their voters' next preference. If no one meets the quota, then the least popular candidate is eliminated and their second preference votes become first preferences. The system continues until all available seats are full.
For example, suppose I voted (1: Nader), (2: Gore), (3: Bush). The election officials tally all the votes and find that Gore has 49 million first preferences, Bush has 50 million, and Nader has 5 million. There's only one presidency, so a candidate would have to have a majority of votes (greater than 52 million out of 104 million) to win. Since no one meets that quota, the lowest ranked candidate gets eliminated - in this case, Nader. My vote now goes to my second preference, Gore. If 4 million Nader voters put Gore second versus 1 million who put Bush second, the tally's now at 53 million Gore, 51 million Bush. Gore has greater than 52 million and wins the election - the opposite result from if we'd elected a president the traditional way.
Another system called Condorcet voting also uses a list of all candidates ranked in order, but uses the information to run mock runoffs between each of them. So a Condorcet system would use the ballots to run a Gore/Nader match (which Gore would win), a Gore/Bush match (which Gore would win), and a Bush/Nader match (which Bush would win). Since Gore won all of his matches, he becomes President. This becomes complicated when no candidate wins all of his matches (imagine Gore beating Nader, Bush beating Gore, but Nader beating Bush in a sort of Presidential rock-paper-scissors.) Condorcet voting has various options to resolve this; some systems give victory to the candidate whose greatest loss was by the smallest margin, and others to candidates who defeated the greatest number of other candidates.
Do these systems avoid the strategic voting that plagues American elections? No. For example, both Single Transferable Vote and Condorcet voting sometimes provide incentives to rank a candidate with a greater chance of winning higher than a candidate you prefer - that is, the same "vote Gore instead of Nader" dilemma you get in traditional first-past-the-post.
There are many other electoral systems in use around the world, including several more with ranking of candidates, a few that do different sorts of runoffs, and even some that ask you to give a numerical rating to each candidate (for example “Nader 10, Gore 6, Bush -100000”). Some of them even manage to eliminate the temptation to rank a non-preferred candidate first. But these work only at the expense of incentivizing other strategic manuevers, like defining “approved candidate” differently or exaggerating the difference between two candidates.
So is there any voting system that automatically reflects the will of the populace in every way without encouraging tactical voting? No. Various proofs, including the Gibbard-Satterthwaite Theorem and the better-known Arrow Impossibility Theorem show that many of the criteria by which we would naturally judge voting systems are mutually incompatible and that all reasonable systems must contain at least some small element of tactics (one example of an unreasonable system that eliminates tactical voting is picking one ballot at random and determining the results based solely on its preferences; the precise text of the theorem rules out “nondeterministic or dictatorial” methods).
This means that each voting system has its own benefits and drawbacks, and that which one people use is largely a matter of preference. Some of these preferences reflect genuine concern about the differences between voting systems: for example, is it better to make sure your system always elects the Condorcet winner, even if that means the system penalizes candidates who are too similar to other candidates? Is it better to have a system where you can guarantee that participating in the election always makes your candidate more likely to win, or one where you can be sure that everyone voting exactly the opposite will never elect the same candidate?
But in practice, these preferences tend to be political and self-interested. This was recently apparent in Britain, which voted last year on a referendum to change the voting system. The Liberal Democrats, who were perpetually stuck in the same third-place situation as Nader in the States, supported a change to a form of instant runoff voting which would have made voting Lib Dem a much more palatable option; the two major parties opposed it probably for exactly that reason.
Although no single voting system is mathematically perfect, several do seem to do better on the criteria that real people care about; look over Wikipedia's section on the strengths and weaknesses of different voting systems to see which one looks best.