On Fri, Jun 28, 2013 at 03:04:13PM +0200, Vidar Wahlberg wrote: > This gave me an idea. > We seem to agree that it's notably the exclusion part that may end up > excluding a party that is preferred by many, but just isn't their first > preference. > I'm sticking to quota election because I don't fully grasp how to apply > other methods (Sainte-Laguë, for instance) to determine when to start > excluding parties. > 1. Give seats to parties exceeding the quota (seats = votes / quota) > 2. Create an ordered list using Ranked Pairs/Beatpath, exclude the least > preferred party and redistribute its votes. Repeat.
Chris, Kristofer. Spending the rest of the day on this, I think I finally understood what you meant with "best formula for apportioning seats in List PR". Or at least I eventually came up with a very simple method, even though it does not meet my concerns about excluding a second preference party that is far more popular than a party that have some more first preference voters. For larger parties who are very likely to get a seat there's neither any reason to create an ordered list, as those parties who do receive one or more seats will never have any votes transfered. Basically, this is what I do: 1. Distribute seats using Sainte-Laguë. 2. If any parties received no seats, exclude the party with least votes and redistribute votes to 2nd preference. 3. Repeat 1-2 until all non-excluded parties got at least 1 seat. Although as noted a party that is a popular as second preference (but less popular as first preference) will easily be excluded, even though more voters would prefer this party over another party. I did implement the other idea I had, setting a quota, distributing seats with "seats = votes / quota" and then redistribute the votes from the least popular party (found using an inversed RP, ranking preference from least to most preferable), regardless of whether the party had received seats or not. It was quite interesting, but there's at least one very unfortunate effect: It could benefit a party to instruct its voters not to set up a party whose voters are likely to set the other party as second preference. For example, party A knowing that voters of party B are likely to put party A as second preference could benefit from having party B excluded early, and thus encourage their voters not to put party B in their preference list. This can of course backfire, leading to neither of the parties winning an extra seat, in the cases where party A are to be excluded before party B. So I'm left with two systems now. One conceptually very simple system that is quite similar to the voting system already used, but a system that won't reflect the preference of the voters very well, only the voters of parties that won't get a seat will have their preference heard. And one system that's far more complex and possibly more open for tactical voting, but reflects the preference of the voters better as the preference of all voters will be heard. -- Regards, Vidar Wahlberg ---- Election-Methods mailing list - see http://electorama.com/em for list info
