ACNielsen: 51 to 49 in Labor’s favour (or is it 50-50?)

Last weekend’s ACNielsen’s monthly poll of 1409 voters was published in this morning’s Fairfax press (here and here).
In two-party preferred terms Labor was two points ahead on 51 to 49 per cent. The previous ACNielsen poll had it at 52 to 48 in Labor’s favour.
Labor’s primary vote was 39 per cent and the Coalition received 43 per cent (both level with the previous poll). The Greens were steady on 10 per cent, the Democrats on 2 per cent, and Family First on 1 per cent.
Howard’s performance rating was steady on 53 per cent. Beazley’s dropped six points to 49 per cent.
Howard maintained a lead of 52 per cent to 38 per cent as preferred prime minister.
ACNielsen also had a look at the Costello option. According to the Age,
The comparison between Mr Costello and Mr Beazley as preferred PM confirms that Mr Costello has a problem with support from the young. He leads Mr Beazley 46-43 per cent among those over 55, but trails 36 to 52 per cent among the youngest voters.
Mr Howard leads Mr Beazley among these same voters by 48-44 per cent.
Fewer voters say they would be more likely to vote Coalition under Mr Costello than a year ago (20 per cent compared with 24 per cent in May 2004).
But there are also fewer saying they would be less likely to vote Coalition (37 per cent to 41 per cent).
According to the SMH, “63 per cent said they expected the Prime Minister to see out the term - a 19 percentage point rise compared with when voters were asked a similar question last September, just before the federal election.”
Why is ACNielsen to the left of Morgan and Newspoll?
If you look at the polling graphs since the 2004 election over recent months, typically ACNielsen has reported a poorer two-party preferred outcome for the Coalition than the other polling organisations.
In large measure this reflects ACNielsen’s approach to attributing preferences on the basis of their polling information. Newspoll and Morgan have been attributing preferences on the basis of the distribution at the last election. In recent elections, non-Coalition-non-Labor voters have been more inclined to preference the Coalition than the opinion polls have reported. (See my earlier discussion on this phenomenon here and here).
By way of example, in the following table I have adjusted ACNielsen’s two-party preferred poll results over recent months to reflect a 38.6 per cent flow to the Coalition of non-Coalition-non-Labor preferences, as was exhibited at the last election.
| Poll date | Published Coalition TPP Result | Adjusted Coalition TPP Result |
| January 2005 | 57 | 57 |
| February 2005 | 52 | 54 |
| March 2005 | 48 | 49 |
| April 2005 | 48 | 50 |
| May 2005 | 49 | 50 |
The adjusted two-pqrty preferred result is 50 per cent each for the Coalition and Labor, and unchanged from the previous ACNeilsen poll in early April.
With the exception of the January result (against the backdrop of the Latham implosion), the adjusted two-party preferred results are much more consistent with the other polls. (Just as ACNielsen’s primary vote results for the Coalition and Labor are consistent).