Brad Ideas - Mutliple candidate voting - Comments

See the comment above

brad — Fri, 06 Jul 2007 13:22:25 -0700

Ping’s link above has some good material on problems with STV.

Now the reality is that all the systems fail (if they need to provide just one winner) and most of the failures are in somewhat pathological cases, but some fail more than others, so it is better to use systems that fail less often in real cases, as well as systems that are easier to understand. Approval is easiest to understand and implement. Condorcet is also fairly easy to understand (except in ties.) Weighted systems are probably too complex for too many voters.

It is however worth noting that some of the “failures” are definitional. For example, the Condorcet Criterion (that the winner beats everybody else in a head to head race) is not met by many of the non-Condorcet systems. Some systems will choose a winner who is everybody’s 2nd choice and others won’t, and it’s subjective if this is a bug or a feature. (IRV does not choose a candidate who is everybody’s 2nd choice but few people’s first choice, while it does choose that candidate if they are not last in the first round.) Some criteria, like monotonicity make sense to everybody, and IRV fails this. Supporters of IRV just feel it has other virtues to make up for the non-monotonicity. However, IRV is inferior to Condorcet in all criteria. See Voting system.

reference?

Platypus — Thu, 05 Jul 2007 18:14:18 -0700

> The most widely known preferential ballot is Single Transferable Vote and its cousin the instant-runoff.
> Many election theorists, however view these as the worst possible system.

Can you give me a reference for this? You correctly point out that STV is pretty complicated and can confuse voters; does it have worse problems than that? Several countries are using it; if there are serious problems it seems like someone should have run into an example by now.

Wikipedia notes that strange things can happen if a party fields too many or too few candidates, but (particularly in the case of presidential elections!) this doesn't seem like a serious bug.

I'm also long a fan of

Ping — Tue, 19 Jun 2007 12:46:54 -0700

I'm also long a fan of approval, as you know.

Condorcet methods have the slight advantage that if you rank two candidates the same, it's no problem.

Mutliple candidate voting

brad — Mon, 18 Jun 2007 15:38:40 -0700

Continuing our discussion of the goals of voting systems, today I want to write about ballots that let you vote for more than one candidate in the same race. Many people have seen Preferential voting where you rank the candidates in order of how much you like them. This is used in Australia, and many private elections such as for the Hugo Awards. The most widely known preferential ballot is Single Transferable Vote and its cousin the instant-runoff. Many election theorists, however view these as the worst possible system. I prefer the Condorcet method with the modification that the cases where it fails, it is declared a tie, or a second type of election is used to break the tie. While it has been demonstrated that all preferential ballots have failure modes where they choose somebody that seems illogical based on the voters’ true desires, this does not have to be true when a tie is possible.

Multiple candidate votes would provide a dramatic improvement in the US — they are already used in many other places. They would have entirely eliminated the question of minor candidates “splitting” or spoiling the vote. There would have been no question in Florida of 2000, with Al Gore defeating George W. Bush (and at least by the popular vote, some feel that Bill Clinton would have lost to George Bush the elder, and there’s strong evidence the electoral margin would have at least been smaller.) This is in fact what prevents them from being used — there is always somebody in power who is going to conclude they would have lost has there been a multi-candidate ballot in place. Such people will fight it harder than advocates push it.

Small party candidates want it because it gives them a chance to be heard. Voters who like them can safely express that preference without fear of “spoiling” the race among the frontrunners. Given that, small candidates can eventually become frontrunners. In the 2 party system, as we’ve seen, any time a minor candidate like Ralph Nader gets popular enough that he might actually make a difference, the result is cries of “Ralph, don’t run” and a dropping of support from those who fear that problem.