Imperfect Voting Systems

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.

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.

"try to resist getting in those good, solid digs if you can possibly avoid it"

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.

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.

The two theorems you quoted technically don't apply to range voting...

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 system that was voted on, which is different from STV, which is the system that the Lib Dems actually support), because there'd be less tactical voting. While electoral reform is tempting for the Lib Dems in part because the current system is biased against them and any other small parties, there's also the fact that a lot of people joined the Lib Dems because they are the only major party supporting electoral reform -- for a lot of Lib Dems getting the party into government is at least in part a means to the end of getting the electoral system changed, rather than changing the electoral system being a means to the end of getting the party into government.

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 Nader has the least number of first preferences, my vote contributes towards Gore's total. In no way does voting Gore > Nader > Bush instead help Gore (in the case where Nader obviously has a small number of votes), but it does make it less likely that Nader will get elected, which I presumably don't want.

The link describes how if your preferences are A > B > C > D, it is sometimes best to vote C > A > B > D because this will help get A elected, which is different to voting Gore ahead of Nader to get Gore elected.

(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 (manipulation), as the total number of votes cast in any one election is variable. This could be extended to different types of election; perhaps, an initial equal allocation of 10 votes per year each, to be cast on any election of my choice, whenever I choose. I might just get to spend all of my 500 votes, saved up from 50 years of not voting for local and regional representatives, on a referendum to make one meaningful change to the system itself.

Sorry, this is a hobby horse of mine: the goods market offers bountiful choice, but unfairly allocates the number of spendable votes; the political market fairly allocates the number of votes, but never offers any choice of when and what these may be spent on. Does not appear that either system is democratic in any meaningful sense.

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 the buttons saying “Niederlande”, “Türkei”, … to switch between different voting systems. The picture on the left is the actual distribution of the seats.) This is a nice illustration of how strongly a voting system changes the result, even without the influence of strategic votes. (For example, the conservative party (in black) would receive between 34 and 73 per cent of the vote.)

(And for any German-speaking folks who are interested, here's a description of the different voting systems in that comparison.)

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 whole. Indeed, it seems quite wrong to suggest, in the context of Parliamentary elections, that a "fair" voting system is the one that minimises tactical voting, as that will merely mean that the "tactical voting" will go on in Parliament itself, in terms of building coalitions of parties rather than coalitions of voters.

Electoral design needs to be looked at in terms of the whole system, not merely candidate selection.

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.

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.

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, you can create a Condorcet system that doesn't have that problem.

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.

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(Writing this was stupid, so I've deleted it.)