Single Transferable Vote Explained

[Yeovil Saint]

If the Lib Dems hold the balance of power on Friday morning, electoral reform will be their main demand to join a coalition government. Single Transferable Vote (STV) is hideously complicated to explain in the abstract, but pretty easy (if longwinded) to explain in practice. So here's a real example, the Dublin Central seat in the Republic of Ireland General Election 2007

 

Dublin Central elects 4 Deputies so each party could nominate 4 candidates, but in practice parties only nominate the maximum that they think they could get elected. So the candidates were:

 

Christian Solidarity: O'Loughlin

Fathers Rights: Beirne

Fianna Fáil: Ahern, Brady, Fitzpatick

Fine Gael: Donohoe

Green: McKenna

Immigration Control: Talbot

Labour: Costello

Progressive Democrats: Hannon

Sinn Féin: McDonald

Independents: Gregory, Perry

 

Ahern, Costello and Gregory were incumbent deputies, Fitzpartick's father was the 4th incumbent who was retiring. Fianna Fáil normally put up 2 candidates in Dublin Central but with them running high in the polls decided to try for 3 seats this time.

 

Each voter could rank the candidates in 1, 2, 3, etc order, they don't have to rank all candidates, as we'll see.

 

First Count

Just as in our First past the post elections the votes are counted, only the first preferences matter at this stage

 

Ahern (FF) 12,734

Gregory (Ind) 4,649

Costello (Lab) 4,353

Donohoe (FG) 3,302

McDonald (SF) 3,182

McKenna (GP) 1,995

Fitzpatrick (FF) 1,725

Perry (Ind) 952

Brady (FF) 939

O'Loughlin (CS) 260

Talbot (IC) 239

Hannon (PD) 193

Beirne (FR) 116

 

34,629 valid votes were cast which made the quota 6,928 - that's because if 4 candidates each received 6,928 votes, the most a 5th candidate could get is 6,927 so 6,928 guarantees election.

 

Ahern as leader of Fianna Fáil easily got elected with many more votes than he needed, so the 2nd count is to reallocate his surplus vote. He needed 6,928, got 12,734 so each vote for him is now counted as 0.544 of a vote. The remaining 0.456 of a vote gets reallocated to their 2nd preferences.

 

Second Count - reallocation of Ahern's surplus

Ahern (FF) ELECTED

Gregory (Ind) 5,453 (+804)

Costello (Lab) 4,793 (+440)

McDonald (SF) 3,471 (+289)

Donohoe (FG) 3,441 (+139)

Brady (FF) 3,342 (+2,403)

Fitzpartick (FF) 3,087 (+1,362)

McKenna (GP) 2,116 (+121)

Perry (Ind) 1,058 (+106)

O'Loughlin (CS) 269 (+9)

Talbot (IC) 253 (+14)

Hannon (PD) 226 (+33)

Beirne (FR) 202 (+86)

 

As expected Ahern's surplus benefited his party colleagues Fitzpartick and Brady although all the candidates got some 2nd preference votes from Ahern voters. No-one's reached the quota now so we start knocking out the bottom candidates, normally you would only eliminate the candidate with the least votes, but in this case even if O'Loughlin ended up with all the votes of Talbot, Hannon and Beirne, he would only have 950 votes, not enough to avoid elimination himself. So the bottom four candidates are all excluded at this stage and their votes passed down to the next preference.

 

If someone had voted Hannon 1 and Ahern 2 then that vote would pass on to a 3rd preference. If someone had voted Ahern 1 and Beirne 2 then that vote is still only worth 0.456 because 0.544 of a vote was used up getting Ahern elected.

 

Third Count - Transfer of O'Loughlin, Talbot, Hannon and Beirne votes.

Ahern (FF) ELECTED

Gregory (Ind) 5,622 (+169)

Costello (Lab) 4,870 (+77)

Donohoe (FG) 3,548 (+107)

McDonald (SF) 3,519 (+48 )

Brady (FF) 3,510 (+168 )

Fitzpartick (FF) 3,236 (+149)

McKenna (GP) 2,221 (+105)

Perry (Ind) 1,133 (+75)

 

Out of that count, 52 votes weren't transferred because they had run out of preferences. The distribution of the minor candidates didn't change much and Perry is the next to be eliminated.

 

Fourth Count - Transfer of Perry's votes

Ahern (FF) ELECTED

Gregory (Ind) 6,062 (+440)

Costello (Lab) 5,028 (+158 )

McDonald (SF) 3,744 (+225)

Donohoe (FG) 3,600 (+52)

Brady (FF) 3,510 (+44)

Fitzpartick (FF) 3,330 (+94)

McKenna (GP) 2,294 (+73)

 

47 of Perry's votes weren't reallocated, and McKenna didn't do well enough to avoid being eliminated at this stage. The fifth count will be vital to Brady and Fitzpartick because one of them might end up bottom where they probably have a lot of transfers to each other.

 

Fifth Count - Transfer of McKenna's votes.

Ahern (FF) ELECTED

Gregory (Ind) 6,799 (+737)

Costello (Lab) 5,809 (+781)

McDonald (SF) 3,948 (+204)

Donohoe (FG) 3,896 (+296)

Brady (FF) 3,616 (+62)

Fitzpartick (FF) 3,447 (+117)

 

97 of McKenna's votes weren't transferred, the Green's 2nd preferences went mainly to the Independent and Labour candidates (interesting that the Greens ended up forming a coalition with Fianna Fáil). Fitzpartick ended up being eliminated which was great news for Brady as we'll see in the sixth count.

 

Sixth Count - Transfer of Fitzpartick's votes

Ahern (FF) ELECTED

Gregory (Ind) 7,385 (+586)

Costello (Lab) 6,073 (+264)

Brady (FF) 5,608 (+1,992)

Donohoe (FG) 4,147 (+251)

McDonald (SF) 4,120 (+172)

 

182 votes were not transferred. Brady gets a boost from voters that presumably voted Fianna Fáil 1, 2 and 3 and now looks favourite to get elected. Gregory passes the quota. Normally when a candidate passes the quota this late they only pass it by an amount that won't change the outcome but in this case the gap between Donohoe and McDonald is so small that re-allocating Gregory's surplus could matter. Because Gregory only needed 6,928 and he's got 7,385 votes 0.062 per vote can be reallocated.

 

So if you voted for Perry 1, McKenna 2, Gregory 3, Costello 4, your vote ends up being 0.938 for Gregory and 0.062 for Costello because neither Perry or McKenna could be elected.

 

If you voted for Ahern 1, Gregory 2, Fitzpartick 3, Brady 4, then your vote has already helped get Ahern elected, so your vote counts as 0.544 for Ahern, 0.428 for Gregory and the remaining 0.028 can't go to Fitzpartick because she's out, so it goes to Brady.

 

Seventh Count - reallocation of Gregory's surplus

Ahern (FF) ELECTED

Gregory (Ind) ELECTED

Costello (Lab) 6,205 (+132)

Brady (FF) 5,764 (+156)

Donohoe (FG) 4,216 (+69)

McDonald (SF) 4,178 (+58 )

 

42 votes weren't reallocated, McDonald didn't get enough transfers to overtake Donohoe so she's eliminated and her votes transferred.

 

Eighth Count - Transfer of McDonald's votes

Ahern (FF) ELECTED

Gregory (Ind) ELECTED

Costello (Lab) 8,018 (+1,813)

Brady (FF) 6,348 (+584)

Donohoe (FG) 4,556 (+340)

 

1,441 of McDonald's votes aren't reallocated because they have run out of preferences - out of the original 13 names on the ballot paper there's only 3 left that can be allocated any votes.

 

Costello's easily elected but his surplus wouldn't be enough for Donohoe to overtake Brady for the 4th seat so Donohoe's eliminated and Brady gets elected as the last candidate.

 

That is all very long-winded but the result's fair. Fianna Fáil got 44.4% of the first preference votes and they got 2 out of the 4 seats, Gregory and Labour got 13.4% and 12.6% and they each got 1 seat, Fine Gael and Sinn Féin got 9.5% and 9.2% and just missed out. Overall the Fianna Fáil voters just prefered Brady to Fitzpartick so he got elected, the voters wouldn't have that much power in a list election.

Edited 2 May, 2010 by Yeovil Saint

[Wes Tender]

If the Lib Dems hold the balance of power on Friday morning, electoral reform will be their main demand to join a coalition government. Single Transferable Vote (STV) is hideously complicated to explain in the abstract, but pretty easy (if longwinded) to explain in practice. So here's a real example, the Dublin Central seat in the Republic of Ireland General Election 2007

 

Dublin Central elects 4 Deputies so each party could nominate 4 candidates, but in practice parties only nominate the maximum that they think they could get elected. So the candidates were:

 

Christian Solidarity: O'Loughlin

Fathers Rights: Beirne

Fianna Fáil: Ahern, Brady, Fitzpatick

Fine Gael: Donohoe

Green: McKenna

Immigration Control: Talbot

Labour: Costello

Progressive Democrats: Hannon

Sinn Féin: McDonald

Independents: Gregory, Perry

 

Ahern, Costello and Gregory were incumbent deputies, Fitzpartick's father was the 4th incumbent who was retiring. Fianna Fáil normally put up 2 candidates in Dublin Central but with them running high in the polls decided to try for 3 seats this time.

 

Each voter could rank the candidates in 1, 2, 3, etc order, they don't have to rank all candidates, as we'll see.

 

First Count

Just as in our First past the post elections the votes are counted, only the first preferences matter at this stage

 

Ahern (FF) 12,734

Gregory (Ind) 4,649

Costello (Lab) 4,353

Donohoe (FG) 3,302

McDonald (SF) 3,182

McKenna (GP) 1,995

Fitzpatrick (FF) 1,725

Perry (Ind) 952

Brady (FF) 939

O'Loughlin (CS) 260

Talbot (IC) 239

Hannon (PD) 193

Beirne (FR) 116

 

34,629 valid votes were cast which made the quota 6,928 - that's because if 4 candidates each received 6,928 votes, the most a 5th candidate could get is 6,927 so 6,928 guarantees election.

 

Ahern as leader of Fianna Fáil easily got elected with many more votes than he needed, so the 2nd count is to reallocate his surplus vote. He needed 6,928, got 12,734 so each vote for him is now counted as 0.544 of a vote. The remaining 0.456 of a vote gets reallocated to their 2nd preferences.

 

Second Count - reallocation of Ahern's surplus

Ahern (FF) ELECTED

Gregory (Ind) 5,453 (+804)

Costello (Lab) 4,793 (+440)

McDonald (SF) 3,471 (+289)

Donohoe (FG) 3,441 (+139)

Brady (FF) 3,342 (+2,403)

Fitzpartick (FF) 3,087 (+1,362)

McKenna (GP) 2,116 (+121)

Perry (Ind) 1,058 (+106)

O'Loughlin (CS) 269 (+9)

Talbot (IC) 253 (+14)

Hannon (PD) 226 (+33)

Beirne (FR) 202 (+86)

 

As expected Ahern's surplus benefited his party colleagues Fitzpartick and Brady although all the candidates got some 2nd preference votes from Ahern voters. No-one's reached the quota now so we start knocking out the bottom candidates, normally you would only eliminate the candidate with the least votes, but in this case even if O'Loughlin ended up with all the votes of Talbot, Hannon and Beirne, he would only have 950 votes, not enough to avoid elimination himself. So the bottom four candidates are all excluded at this stage and their votes passed down to the next preference.

 

If someone had voted Hannon 1 and Ahern 2 then that vote would pass on to a 3rd preference. If someone had voted Ahern 1 and Beirne 2 then that vote is still only worth 0.456 because 0.544 of a vote was used up getting Ahern elected.

 

Third Count - Transfer of O'Loughlin, Talbot, Hannon and Beirne votes.

Ahern (FF) ELECTED

Gregory (Ind) 5,622 (+169)

Costello (Lab) 4,870 (+77)

Donohoe (FG) 3,548 (+107)

McDonald (SF) 3,519 (+48 )

Brady (FF) 3,510 (+168 )

Fitzpartick (FF) 3,236 (+149)

McKenna (GP) 2,221 (+105)

Perry (Ind) 1,133 (+75)

 

Out of that count, 52 votes weren't transferred because they had run out of preferences. The distribution of the minor candidates didn't change much and Perry is the next to be eliminated.

 

Fourth Count - Transfer of Perry's votes

Ahern (FF) ELECTED

Gregory (Ind) 6,062 (+440)

Costello (Lab) 5,028 (+158 )

McDonald (SF) 3,744 (+225)

Donohoe (FG) 3,600 (+52)

Brady (FF) 3,510 (+44)

Fitzpartick (FF) 3,330 (+94)

McKenna (GP) 2,294 (+73)

 

47 of Perry's votes weren't reallocated, and McKenna didn't do well enough to avoid being eliminated at this stage. The fifth count will be vital to Brady and Fitzpartick because one of them might end up bottom where they probably have a lot of transfers to each other.

 

Fifth Count - Transfer of McKenna's votes.

Ahern (FF) ELECTED

Gregory (Ind) 6,799 (+737)

Costello (Lab) 5,809 (+781)

McDonald (SF) 3,948 (+204)

Donohoe (FG) 3,896 (+296)

Brady (FF) 3,616 (+62)

Fitzpartick (FF) 3,447 (+117)

 

97 of McKenna's votes weren't transferred, the Green's 2nd preferences went mainly to the Independent and Labour candidates (interesting that the Greens ended up forming a coalition with Fianna Fáil). Fitzpartick ended up being eliminated which was great news for Brady as we'll see in the sixth count.

 

Sixth Count - Transfer of Fitzpartick's votes

Ahern (FF) ELECTED

Gregory (Ind) 7,385 (+586)

Costello (Lab) 6,073 (+264)

Brady (FF) 5,608 (+1,992)

Donohoe (FG) 4,147 (+251)

McDonald (SF) 4,120 (+172)

 

182 votes were not transferred. Brady gets a boost from voters that presumably voted Fianna Fáil 1, 2 and 3 and now looks favourite to get elected. Gregory passes the quota. Normally when a candidate passes the quota this late they only pass it by an amount that won't change the outcome but in this case the gap between Donohoe and McDonald is so small that re-allocating Gregory's surplus could matter. Because Gregory only needed 6,928 and he's got 7,385 votes 0.062 per vote can be reallocated.

 

So if you voted for Perry 1, McKenna 2, Gregory 3, Costello 4, your vote ends up being 0.938 for Gregory and 0.062 for Costello because neither Perry or McKenna could be elected.

 

If you voted for Ahern 1, Gregory 2, Fitzpartick 3, Brady 4, then your vote has already helped get Ahern elected, so your vote counts as 0.544 for Ahern, 0.428 for Gregory and the remaining 0.028 can't go to Fitzpartick because she's out, so it goes to Brady.

 

Seventh Count - reallocation of Gregory's surplus

Ahern (FF) ELECTED

Gregory (Ind) ELECTED

Costello (Lab) 6,205 (+132)

Brady (FF) 5,764 (+156)

Donohoe (FG) 4,216 (+69)

McDonald (SF) 4,178 (+58 )

 

42 votes weren't reallocated, McDonald didn't get enough transfers to overtake Donohoe so she's eliminated and her votes transferred.

 

Eighth Count - Transfer of McDonald's votes

Ahern (FF) ELECTED

Gregory (Ind) ELECTED

Costello (Lab) 8,018 (+1,813)

Brady (FF) 6,348 (+584)

Donohoe (FG) 4,556 (+340)

 

1,441 of McDonald's votes aren't reallocated because they have run out of preferences - out of the original 13 names on the ballot paper there's only 3 left that can be allocated any votes.

 

Costello's easily elected but his surplus wouldn't be enough for Donohoe to overtake Brady for the 4th seat so Donohoe's eliminated and Brady gets elected as the last candidate.

 

That is all very long-winded but the result's fair. Fianna Fáil got 44.4% of the first preference votes and they got 2 out of the 4 seats, Gregory and Labour got 13.4% and 12.6% and they each got 1 seat, Fine Gael and Sinn Féin got 9.5% and 9.2% and just missed out. Overall the Fianna Fáil voters just prefered Brady to Fitzpartick so he got elected, the voters wouldn't have that much power in a list election.

 

Simplicity itself. Let's go for it. I would expect that the results of the election ought to be in within a month of polling day.

[Badger]

Simplicity itself. Let's go for it. I would expect that the results of the election ought to be in within a month of polling day.

 

And then some bastard demands a second or third recount...

 

This strikes me as a typical wooly headed Liberal policy thought up by some academic sandal wearing tosser.Net result is hung parliaments for evermore with more libs,greens etc gaining a sprinkling of seats,along with some of the extreme right and left.

[Whitey Grandad]

You can't vote for a person so you can't ask that person what their views are. You can vote, but you have no idea who will be representing you.

[Yeovil Saint]

Simplicity itself. Let's go for it. I would expect that the results of the election ought to be in within a month of polling day.

Ireland manage it very easily, they vote on Thursdays as we do, I think they don't count overnight, but start on Friday morning and by tea time 99% of the results are in. Don't know why you think we would be more useless at it.

[Yeovil Saint]

You can't vote for a person so you can't ask that person what their views are. You can vote, but you have no idea who will be representing you.

 

You only vote for the person in STV elections, you don't even have to vote for the party, imagine that you're a Tory, but one of the candidates for election you really don't like, don't like Labour but one of their candidates isn't bad and you want the UKIP guy to be elected but you don't think that he could get in then you can vote for something like this.

 

1. UKIP candidate

2. Tory A

3. Tory B

4. Labour A

5. Lib Dem A

6. Lib Dem B

7. Tory C

8. Lib Dem C

9. Labour B

10. Green

11. BNP

 

Then if UKIP doesn't get their candidate elected, your vote isn't wasted, it goes to the Tory you like most. At the other end of the ranking you would be saying that you prefer anyone to be elected ahead of the BNP candidate.

[ecuk268]

The Alternative Vote system is simpler.

 

The Independent has a fascinating couple of booklets in the paper this weekend about elections, full of interesting facts like - no government has had a majority of the people who voted since 1931.

 

Also, bearing in mind Bigotgate, Winston Churchill once said "The best argument against democracy is a five-minute conversation with the average voter".

[Saintandy666]

Look, let me explain it simpler.

 

1. Everyone ranks as many candidates as they like.(it takes place in multi member constituencies, so say Hampshire could be 1 constituency)

2. There is a threshold for winning a seat, if you pass this threshold on first choice, you are elected.

3. Then the 'excess' votes on the person elected are redistributed proportionally. By this I mean they look at all the 2nd choices of that person and redistribute them proportionally to the amount of excess votes received.

4. If another person has passed the threshold then, the same happens to their 2nd choice votes, if not then you eliminate the bottom person and redistribute their 2nd choice votes.

 

And basically you repeat those steps. This is Politics A level revision for me.

 

Also, they already use it in Ireland, Northern Ireland, Australian Senate elections to name a few... so it does work!!!