PRSTV Irish Voting System technical questions

Mr. Flibble

Does anyone here have a good understanding of the irish system of counting votes - the PRSTV system?

I have a project where I'll have to understand the system. Can anyone point me to an explination of it?

Thanks

ps. if you think there may be a forum more suitable for this question pls let me know.

civdef

There's always google - first two links:

http://en.wikipedia.org/wiki/Single_Transferable_Vote
http://www.politics.ie/wiki/index.php?title=PR-STV

then a bit further down the list:
http://www.electoralofficeni.gov.uk/index/faqs/pr-stv-voting-system-faqs.htm

And of course:
http://www.oasis.gov.ie/government_in_ireland/elections/proportional_representation.html

Mr. Flibble

Cheers

ISAW

Mr. Flibble wrote:

Does anyone here have a good understanding of the irish system of counting votes - the PRSTV system?

I have a project where I'll have to understand the system. Can anyone point me to an explination of it?

Thanks

ps. if you think there may be a forum more suitable for this question pls let me know.

Here is how you work out a quota:
Whats the lowest number of votes a person (to get elected to a single position) can get? Just over half?
What if there are two positions? Well if two get just over a third nobody else can get a third can they? What about four seats? If four get a fifth each then nobody else can get more than them.

So the quota is one over one more the number of seats plus one and then add one to that. i.e.
(1/number to be elected +1) +1

Try it out in a class. Say you have two positions and 30 students
(1/2+1) +1 = One more than a third of the class. so if two people reach 11 (30/3+1) then nobody else can get more then them.

Get eight (can be as many as you like) candidates say and get people to quque up behind the person they want to win. Any queues with eleven (say the person can vote for themselves) automitically get elected.

Heres how transfers work.

People with the least votes get eliminated. so the smaller queues get asked to jump to a different queue. Take a small queue and disband it. Some may go to another queue or may decide not to vote and just sit down. Then you count the queues asgain. Eleven or more than eleven means you get elected.
So you could ask six picked at random from the eighteen to jump to other queuse but Heres how surplus works:

Say candidate A gets electeed but has eighteen rather than eleven. He has seven more than he needs. You ask the whole eighteen who would be their next perference. Say three say candidate B and six say C. Nine wouldnt bother to vote for anyone else. That means half are "non transferable" (the nine of 18) a third are for C and a sixth for B so (the surplus is seven) Half 31/2 is Non transferable 2 1/3 are candidate C and 1 1/6 are B. Depending on the system you can round these up or down. Rounding transfers down C would get 2 votes B two votes and three would be Non transferrable. Rounding down C would get 2 B 1 and non transferrable 4.

In practice most elections deal with thousands of votes not 30. One exception is the Irish Senate Panel votes which has about 900 votes (all the Councillors TDs and senators in the country). so in this election each vote becomes 1000 votes to facilitate doing transfers.

ISAW

Mr. Flibble wrote:

Does anyone here have a good understanding of the irish system of counting votes - the PRSTV system?

I have a project where I'll have to understand the system. Can anyone point me to an explination of it?

Thanks

ps. if you think there may be a forum more suitable for this question pls let me know.

Here is how you work out a quota:
Whats the lowest number of votes a person (to get elected to a single position) can get? Just over half?
What if there are two positions? Well if two get just over a third nobody else can get a third can they? What about four seats? If four get a fifth each then nobody else can get more than them.

So the quota is one over one more the number of seats plus one and then add one to that. i.e.
(1/number to be elected +1) +1

Try it out in a class. Say you have two positions and 30 students
(1/2+1) +1 = One more than a third of the class. so if two people reach 11 (30/3+1) then nobody else can get more then them.

Get eight (can be as many as you like) candidates say and get people to quque up behind the person they want to win. Any queues with eleven (say the person can vote for themselves) automitically get elected.

Heres how transfers work.

People with the least votes get eliminated. so the smaller queues get asked to jump to a different queue. Take a small queue and disband it. Some may go to another queue or may decide not to vote and just sit down. Then you count the queues asgain. Eleven or more than eleven means you get elected.
So you could ask six picked at random from the eighteen to jump to other queuse but Heres how surplus works:

Say candidate A gets electeed but has eighteen rather than eleven. He has seven more than he needs. You ask the whole eighteen who would be their next perference. Say three say candidate B and six say C. Nine wouldnt bother to vote for anyone else. That means half are "non transferable" (the nine of 18) a third are for C and a sixth for B so (the surplus is seven) Half 31/2 is Non transferable 2 1/3 are candidate C and 1 1/6 are B. Depending on the system you can round these up or down. Rounding transfers down C would get 2 votes B two votes and three would be Non transferrable. Rounding down C would get 2 B 1 and non transferrable 4.

In practice most elections deal with thousands of votes not 30. One exception is the Irish Senate Panel votes which has about 900 votes (all the Councillors TDs and senators in the country). so in this election each vote becomes 1000 votes to facilitate doing transfers.

Mr. Flibble

ISAW wrote:

Say candidate A gets electeed but has eighteen rather than eleven. He has seven more than he needs. You ask the whole eighteen who would be their next perference. Say three say candidate B and six say C. Nine wouldnt bother to vote for anyone else. That means half are "non transferable" (the nine of 18) a third are for C and a sixth for B so (the surplus is seven) Half 31/2 is Non transferable 2 1/3 are candidate C and 1 1/6 are B. Depending on the system you can round these up or down. Rounding transfers down C would get 2 votes B two votes and three would be Non transferrable. Rounding down C would get 2 B 1 and non transferrable 4.

Can you verify that this is why rule used in ROI. I was told that only the surplus votes were moved to the next round - not an average of all the votes.

my understanding was this:
say there are 3 candidates and the quota is 10.
the votes get put into 3 piles according to the 1st preference.
candA has 15 votes.

the 5 surplus votes get moved to the next round based on the 2nd preference.

which means that the outcome of the election can be different depending on the random choice of ordering the votes in a pile (which is why the votes are marked through out the election so recounts can be done).

Macy

Mr. Flibble wrote:

I was told that only the surplus votes were moved to the next round - not an average of all the votes.

which means that the outcome of the election can be different depending on the random choice of ordering the votes in a pile (which is why the votes are marked through out the election so recounts can be done).

This is how the system works, and could've been a benefit of e-voting that proportional "surplus" could be distributed. However, the Government didn't put this in the legislation or the software spec (imo to make it much harder for any paper trail to be effective).

ISAW

Mr. Flibble wrote:

Can you verify that this is why rule used in ROI. I was told that only the surplus votes were moved to the next round - not an average of all the votes.
...
which means that the outcome of the election can be different depending on the random choice of ordering the votes in a pile (which is why the votes are marked through out the election so recounts can be done).

Off the top of my head
The actual rules are in Schedule two or three of the 1923 or 1937 Elections act. go to the government Atourney generales site i think it is Irishstatutebook.ie. Look up (i mean search under ) Elections Act AND Dáil Then llok through the Schedules . They deal with registration and with voting systems and counting votes.

The example was a classroom
From practical experience I can tell you that SOMETIMES the whole pile of votes is counted. SAy in a first count the poll topper has a surplus. Then it is quite easy to count ALL the candidates number two's.

But if on the tenth count say a candidate gets elected with a surplus than the votes he now has may include number nines eights sevens etc.

In practice the last packet of transfers is usually taken. This may be problemmatic. Say for example a Sinn Fein candidate gets elected with a 500 surplus and there are three candidates just under the quota with two more to be elected. . Say they are all about 150 short and the Sinn Fein guy has 500 votes and 300 go to one candidate say a socialist. 50 to the other two candidates and 100 non transferable. Then say there is a Labout and PD left and both are about 100 votes short of a quota. The Socialist surplus is now distributed. It is 150. But it is usually done by the last packet (the 500 sinn fein votes). Now since 100 were non transfers 20 % are NT But of the other perferences on the SF papers it is more likely that the next perference would be Labout or left than PD or right. So rather than a 50/50 split one might get a 80 /20 split and the PD not get elected because the 500 vote sample was from a left wing candidate.

It is a valid criticism. Technically one could argue ALL the SF votes should be counted and not the 500 surplus. I should actually add something here. Lets say the SF guy just got elected from transfers from anoither SF elimination. Then the packet is probably biased in favour of the left. But if hew got elected from a CSP or PD elimination then the surplus would be biased to the right.
So it isnt the gut who just went over it is where the last transfers he got came from.

Correct me anyone if I am wrong.

Mr. Flibble

Thanks. Think I've got my head around it all now.

ISAW

ISAW wrote:

Off the top of my head
The actual rules are in Schedule two or three of the 1923 or 1937 Elections act.

This is wrong! Correction. the word is "electoral" Electoral Act. they are the ones about running elections.