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Archive for February, 2010

A busy week for political polls. After the release of the Roy Morgan Research poll on Friday (already covered in the previous update on Sunday,) there were two additional polls released on Sunday night by TV3 (Reid Research poll) and One News (Colmar Brunton poll).

The Colmar Brunton poll shows increases in support for National (54%, up 1%) as well as Labour (34%, up 3%) relative to the last Colmar Brunton poll published in late November 2009. The big loser appears to be the Green party (4.7%, down 2.3%). None of the changes are statistically significant on their own. The TV3 poll also shows no significant changes relative to the last TV3 poll published in mid December 2009.

It’s been a slow start to year for NZ political polling, but now that we finally have a handful of polls it’s interesting to look at some of the trends. Please see below the graphs for analysis.

As usual, the two graphs below summarise the polling averages for the party vote after the new poll. The horizontal axes represent the date, starting 60 days before the 2005 NZ General Election, and finishing 60 days from the present. The solid lines with grey error bands show the moving averages of the party vote for each party, and circles show individual polls with the vertical lines representing the total errors.

Party vote support for the eight major and minor NZ political parties

Party vote support for the eight major and minor NZ political parties as determined by moving averages of political polls. Colours correspond to National (blue), Labour (red), Green Party (green), New Zealand First (black), Maori Party (pink), ACT (yellow), United Future (purple), and Progressive (light blue) respectively. Party vote support for the six minor NZ political parties

Party vote support for the six minor NZ political parties

Party vote support for the six minor NZ political parties as determined by moving averages of political polls. Colours correspond to Green Party (green), New Zealand First (black), Maori Party (pink), ACT (yellow), United Future (purple), and Progressive (light blue) respectively.

As always, please check the Graphs page for further simulation results.

Since it’s been a while, I’ll discuss the results for each party below.

  • Green Party: In previous posts I’ve pointed out that “there appears to be a roughly 6% chance that the Green party will fail to clear the 5% party vote threshold and therefore get no seats in Parliament.” In fact, at one stage in the last month the simulation was predicting an 11% chance this would happen. In hindsight, this appears (as predicted in the relevant post) to be the result of statistical errors on the polling averages blowing up due to the small number of polls released early this year. With the release of three polls in the last week the Green Party’s polling averages have moved from 5.7% +- 0.5% in early February to 6.3% +- 0.3% currently. The small increase coupled with the tighter margin of error now means the Green Party are predicted to have a greater than 99.9% chance of getting seats in Parliament.
  • New Zealand First: I’m not sure if anybody picked up on it, but at one stage the New Zealand First party were predicted to have a roughly 1% chance of clearing the 5% party vote threshold and winning six seats seats in Parliament.  The reason for this appears to be the same as that given for the Green Party above; statistical errors on the polling averages blowing up due to the small number of polls.  After rerunning the simulation with the latest polls added in to the calculations I am able to confirm that at no stage were the New Zealand First party predicted to win any seats in Parliament.
  • National: A couple of recent polls have shown National to be in the low-50% range, a reasonable drop off their polling highs in the middle of 2009. At one stage I was almost ready to call TOD on the National Honeymoon (to the extent that the term “Honeymoon” has any meaning.) The last two polls from One News and TV3 have bumped National back up to the mid 50% range, however. Current averages have the National party on 54.0% +- 1.1%; a significant, although small, decrease relative to the post-election high of 56.3% +- 0.9% recorded on the 10th of October 2009.
  • Labour: Labour’s moving average currently has them on 31.9% +- 0.8%; a small but significant rise compared to their post-election low of 28.9% +- 0.7% on the 23rd February 2009.
  • Others: The ACT Party and the Maori Party have been consistently polling around the 2% mark for the last six months. Current polling puts support at 1.7% +- 0.3%, and 2.4% +- 0.3% respectively. The Progressive Party and United Future NZ have been consistently polling around the 0.2% mark for the last six months. The relative errors on these averages for the Progressive Party and United Future NZ are the largest of any of the parties due to significant rounding errors in the polls; most pollsters only report results rounded to the nearest 0.5%. Both parties are polling below 0.6% at the 90% confidence level.

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The latest NZ political poll was released by Roy Morgan on Friday, February 19. The poll shows an increase in support for the Green party of 2% points and drop in support for the New Zealand First party of 1.5% points relative to the latest Roy Morgan Research poll released two weeks ago. For the other parties the changes are not statistically significant.

As usual, the two graphs below summarise the polling averages for the party vote after the new poll. The horizontal axes represent the date, starting 60 days before the 2005 NZ General Election, and finishing 60 days from the present. The solid lines with grey error bands show the moving averages of the party vote for each party, and circles show individual polls with the vertical lines representing the total errors.

Party vote support for the eight major and minor NZ political parties

Party vote support for the eight major and minor NZ political parties as determined by moving averages of political polls. Colours correspond to National (blue), Labour (red), Green Party (green), New Zealand First (black), Maori Party (pink), ACT (yellow), United Future (purple), and Progressive (light blue) respectively.

Party vote support for the six minor NZ political parties

Party vote support for the six minor NZ political parties as determined by moving averages of political polls. Colours correspond to Green Party (green), New Zealand First (black), Maori Party (pink), ACT (yellow), United Future (purple), and Progressive (light blue) respectively.

As always, please check the Graphs page for further simulation results.

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The latest NZ political poll was conducted by DigiPoll and released by the Herald on February 13. The poll does not show significant changes in support for any of the parties relative to the last Herald-DigiPoll released in late October 2009, and does not significantly alter the polling averages calculated after the latest Roy Morgan Research poll 10 days ago.

As usual, the two graphs below summarise the polling averages for the party vote after the new poll. The horizontal axes represent the date, starting 60 days before the 2005 NZ General Election, and finishing 60 days from the present. The solid lines with grey error bands show the moving averages of the party vote for each party, and circles show individual polls with the vertical lines representing the total errors.

Party vote support for the eight major and minor NZ political parties

Party vote support for the eight major and minor NZ political parties as determined by moving averages of political polls. Colours correspond to National (blue), Labour (red), Green Party (green), New Zealand First (black), Maori Party (pink), ACT (yellow), United Future (purple), and Progressive (light blue) respectively.

Party vote support for the six minor NZ political parties

Party vote support for the six minor NZ political parties as determined by moving averages of political polls. Colours correspond to Green Party (green), New Zealand First (black), Maori Party (pink), ACT (yellow), United Future (purple), and Progressive (light blue) respectively.

As always, please check the Graphs page for further simulation results.

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The latest NZ political poll was released by Roy Morgan on Friday, February 5. The poll does not show significant changes in support for any of the parties relative to the last Roy Morgan poll from late January.

As usual, the two graphs below summarise the polling averages for the party vote after the new poll. The horizontal axes represent the date, starting 60 days before the 2005 NZ General Election, and finishing 60 days from the present. The solid lines with grey error bands show the moving averages of the party vote for each party, and circles show individual polls with the vertical lines representing the total errors.

Party vote support for the eight major and minor NZ political parties

Party vote support for the eight major and minor NZ political parties as determined by moving averages of political polls. Colours correspond to National (blue), Labour (red), Green Party (green), New Zealand First (black), Maori Party (pink), ACT (yellow), United Future (purple), and Progressive (light blue) respectively.

Party vote support for the six minor NZ political parties

Party vote support for the six minor NZ political parties as determined by moving averages of political polls. Colours correspond to Green Party (green), New Zealand First (black), Maori Party (pink), ACT (yellow), United Future (purple), and Progressive (light blue) respectively.

As always, please check the Graphs page for further simulation results.

Based on the recent polling results there appears to be a roughly 6% chance that the Green party will fail to clear the 5% party vote threshold and therefore get no seats in Parliament. Obviously this is partially attributable to the Greens drop in polling (6%, down 2%,) but is also largely due to the statistical errors on the polling averages blowing up due to the small number of polls over the last two months or so. Again, the Green’s polling result does not represent a statistically significant change from the last poll, so this result may very well change due to future polling.

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One of the major goals of this site is to try and predict election results based on recent relevant political polling. This is intended to include not just the total number of seats won by each party, but also viable coalition possibilities and electorate level results.

Today I present the simulation results at the candidate level, including probabilities for each major or minor party candidate to be elected to parliament by either winning an electorate or being selected off their party list. First though, in the interests of disclosure, I thought I should release the data I’m using for the party lists. The 2008 Party Lists are available in MS Excel (.xlsx) format [82kB].

The simulation requires the party lists to be input in the form of a list linking each candidate to the electorate they stood for (or else indicating they were a list only candidate.) The list is based largely on the information on the Party lists for the 2008 General Election page on the Elections New Zealand website, and the electorate information from the Candidates by electorate page from Wikipedia, and is amended at discretion.

The data format is as follows:

  1. Party Code : A unique code for each political party.  Parties are numbered 0~7, and ordered firstly by the number of seats won in the 2008 NZ General Election, and secondly by the number of party votes received.
  2. Party
  3. List Ranking
  4. Name : The name of the candidate as given on the Elections New Zealand website.
  5. Electorate : The electorate the candidate stood in. For list-only candidates this will read “list only.”
  6. Electorate Code : A unique code for the electorate.  Electorates are numbered in alphabetical order, with general electorates (#0 ~ #62) preceding Maori electorates (#63 ~ #69). If the candidate is a list-only candidate candidate this code will take the value -1.

For computational reasons each major or minor party candidate standing in an electorate must have a list ranking. In order to avoid having this requirement affect the results the lists are simply extended to 100 candidates for each party, with electorate-only candidates placed in the lowest ranked positions such that they will never be elected to a list seat. The intermediate positions are then filled with dummy candidates: for example, the candidate “NAT-74-list only” refers to the 74th ranked candidate on the National Party list, with the “list only” suffix indicating that they are a list-only candidate. Please feel free to use or amend the file at will. Corrections gratefully accepted.

The current simulation, however, does not use the 2008 Party Lists. Instead it references an alternative list that has been amended to take into consideration changes during the current term of Parliament. This current list used for the simulation is also available in MS Excel (.xlsx) format [82kB]. A summary of changes is as follows:

  1. Labour : The list reflects the retirements of Helen Clark and Michael Cullen during the term of Parliament. Candidates ranked #3 (Phil Goff) onwards are moved up two list places each. Current Parliamentary members are moved up in the list ahead of unsuccessful candidates (ahead of list candidate #42 Judith Tizard). A new candidate replacing Helen Clark (David Shearer, Mount Albert) is included, ranked #41 and inserted into the list ahead of Judith Tizard. A new dummy list candidate (“LAB-77-list only”) is inserted in position #77 in place of Michael Cullen.
  2. National : Richard Worth (unsuccessful candidate for Epsom, list rank #23) is removed, and subsequent candidates are moved up one rank. A new dummy candidate for Epsom (“NAT-67-Epsom”) is inserted in position #67 in his place.
  3. Green : Jeanette Fitzsimons (list-only candidate, list rank #1) and Sue Bradford (candidate for East Coast Bays, list rank #3) are removed, and subsequent candidates moved up. A new dummy candidate for East Coast Bays (“GRE-66-East Coast Bays”) is inserted in position #66 replacing Sue Bradford. A new dummy list candidate (“GRE-67-list only”) is inserted in position #67 in place of Jeanette Fitzsimons.

The above modifications are only intended to capture the spirit of changes since the beginning of the term of parliament and are of course subject to change when the parties release their official party lists closer to the date of the 2011 General Election. If anybody has any serious objections – or is just curious how things would work out with different party lists – and is willing to provide an updated list in the same format then I would be happy to rerun any simulations.

The candidate level results of the most recent simulation (January 22nd, after the release of the latest Roy Morgan Research poll) are shown in the table below (please click for an enlarged view.)

Probabilities for each candidate to be elected to Parliament

The table gives the probabilities for each candidate to be elected to Parliament by winning an electorate, by being elected from their party list, and an overall probability for either method combined. The “Rank” column gives the respective candidate’s relative likelihood of being elected, and is ordered firstly by probability to be elected, and then by party code and list ranking where there is a tie. Probabilities are rounded to the nearest percent.

The first 89 ranked candidates are guaranteed to be elected, and will of course win 89 seats between them. Candidates ranked 90 through to 114 are considered highly likely to be elected, and each have individual probabilities in the 90% to 100% range. These 25 candidates are expected to win a further 24.6 seats between them, for a cumulative total of 113.6 seats in Parliament. After this we get to the marginal list and electorate candidates: those ranked 115 through to 135 have probabilities in the 10% to 90% range. These 21 candidates are expected to win a further 9.4 seats between them, for a cumulative total of 123.0 seats in Parliament. Next we have 14 more canadidates ranked 136 through to 149 who are considered highly unlikely to be elected to Parliament, with probabilities of less than 10% each. These 14 candidates are expected to win only 0.2 seats between them, bringing the cumulative total to 123.2 seats – an expected overhang of 3.2 seats. Finally, candidates ranked 150 through 800 (many not shown in the table for ease of viewing) have no chance of being elected to Parliament based on current polling data.

I realise that the above calculations may seem little more than trivia at the moment given that we are so far out from the next election, and that the finalised party lists and electorate candidates will not be known for a long time. However, the main motivation for doing this simulation is a hope that people will be able to see which individual list candidate their party vote is likely to be counted for. Closer to the 2011 General Election I will begin publishing “effective party lists” on a regular basis. These effective lists will show only those candidates on the cusp of winning a list seat for each party, and will hopefully give NZ voters a better idea of where their vote is going, and a more meaningful alternative to a quick glance at the top of the lists for each party which some seem to use now when deciding how to cast their votes.

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A few days ago Jeanette Fitzsimons announced her retirement from Parliament, effective February 11th 2009. Ms Fitzsimons will be replaced by Gareth Hughes, who was ranked #11 on the Green Party List for the 2008 NZ General Election.

The implications of this move for the other major and minor NZ political parties are potentially far greater than many would suspect of a simple swapping of list members, something that has already happened three times in the last year alone (Labour list MP Michael Cullen, National list MP Richard Worth, and Green list MP Sue Bradford have all resigned in the last 10 months.) The reason for this is that the new Green MP Gareth Hughes stood for the Ohariu seat in the 2008 General Election, where he had the effect of splitting the vote and allowing United Future MP Peter Dunne’s party in to Parliament through the MMP electorate waiver (Mr. Dunne did not bring any list MP’s with him, however.) Assuming Gareth Hughes contests Ohariu again in a 2011 General Election he will be campaigning as an MP, not as an outsider, which should change the dynamics of the race. BKD has a multi-part series (prologue, part 1, part 2, part 3, part 4, part 5) looking at how this affects the race in Ohariu.

Firstly, before starting with any analysis, I thought I should mention the latest election simulation results from Ohariu: based on the latest polling averages the United Future candidate (presumably current MP Peter Dunne) is expected to win 73.2% of the time, the National Party candidate (presumably current list MP Katrina Shanks) is expected to win 26.7% of the time, and the Labour Party candidate (presumably current list MP Charles Chauvel) is expected to win 0.1% of the time. I wouldn’t put too much faith in these numbers though, as they are computed partially by comparing the current polling averages to the results of the 2005 and 2008 NZ General Elections, and as National as polling considerably higher than they were then the model is behaving a bit pathologically. Additionally, the model does not take the merits of individual candidates into account, instead calculating probabilities for “generic” candidates from each party, and so doesn’t take into account any changes in the dynamics that will occur due to Mr. Hughes’ presence in Parliament.

Rather than focusing on trying to calculate the probabilities for each of the above candidates, I would instead like to investigate the results of an election under two simple scenarios; firstly with Peter Dunne winning Ohariu, and secondly with him losing. The implications of the first scenario are calculated using a MC Simulation of 50,000 NZ Elections with Dunne winning Ohariu. The resulting distributions of seats for National and Labour are shown below.

Histogram showing the total number of seats National are expected to win in parliament under Scenario #1

Histogram showing the total number of seats National are expected to win in parliament under Scenario #1, with Peter Dunne winning the Ohariu electorate. National are expected to win 66.5 +- 1.8 (RMS) seats.

Histogram showing the total number of seats Labour are expected to win in parliament under Scenario #1

Histogram showing the total number of seats Labour are expected to win in parliament under Scenario #1, with Peter Dunne winning the Ohariu electorate. Labour are expected to win 38.6 +- 1.6 (RMS) seats.

Under this scenario, National are expected to pick up a total of 66.5 +- 1.8 seats in Parliament, and Labour a total of 38.6 +- 1.6 seats.

The implications of the second scenario are calculated analogously using a MC Simulation of 50,000 NZ Elections with Peter Dunne not winning Ohariu. The resulting distributions of seats for National and Labour are again shown below.

Histogram showing the total number of seats National are expected to win in parliament under Scenario #2

Histogram showing the total number of seats National are expected to win in parliament under Scenario #2, with Peter Dunne not winning the Ohariu electorate. National are expected to win 66.8 +- 1.8 (RMS) seats.

istogram showing the total number of seats Labour are expected to win in parliament under Scenario #2

Histogram showing the total number of seats Labour are expected to win in parliament under Scenario #2, with Peter Dunne not winning the Ohariu electorate. Labour are expected to win 38.8 +- 1.6 (RMS) seats.

At a casual glance, it may not be easy to see the difference between these two graphs and the ones shown earlier. However, under this scenario, National are expected to pick up a total of 66.8 +- 1.8 seats and Labour a total of 38.8 +- 1.6 seats. The slightly counter-intuitive result of the study is that if Peter Dunne loses the Ohariu seat both National and Labour are individually expected to be slightly better off, and this result holds regardless of which party’s candidate picks up Ohariu in the event that Mr. Dunne loses. The reason for this outcome is that if Peter Dunne loses Ohariu, his party does not achieve the electorate waiver, and as they are also unlikely to acheive the 5% party vote threshold they end up with no seats in Parliament. This effectively creates an extra list seat for National and Labour to fight over. The probability of it falling to one party or the other (or to a minor party) is roughly proportional to their respective party vote totals. The actual results are shown in the table below to two decimal places:

Comparison of total number of seats won in Parliament by each party for two different scenarios

Comparison of total number of seats won in Parliament by each party for two different scenarios; Peter Dunne wins Ohariu, and Peter Dunne loses Ohariu. The right-most column shows the expected difference for each party between the two scenarios.

This raises an interesting problem with regards to election strategy in the Ohariu electorate. If United Future were equally capable of going into coalition with either a Labour-led or National-led coalition, then Labour would be slightly better of if Peter Dunne won the seat, and National slightly worse off. However, as Peter Dunne has made clear, United Future would not be interested in going into coalition with Labour, and so therefore the opposite applies. Labour’s counter-intuitive goal for the Ohariu electorate in the 2011 NZ General Election is not to win, but rather to make sure that the United Future candidate (or ACT or Maori Party candidates, if applicable) do not win. To do otherwise, and vigorously contest the electorate and risk splitting the vote three or more ways, as they did in the 2008 General Election, would be a massive tactical and strategic blunder, and would indicate a poor understanding of the MMP electoral system. Of course, the above conclusion is of limited importance if the the Labour Party are unable to close the 22% point polling gap between themselves and National, but could be crucial in determining the results of a closer election.

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