Tuesday, April 30, 2013

Weekly aggregation: 44.3 to 55.7

This week we have two fresh polls ready for Bayesian aggregation:

  • The Morgan poll moved 2.5 percentage points in the Coalition's favour (56.5 to 43.5)
  • The Essential poll was unmoved on the previous independent fortnight (54 to 46), but it is a percentage point in the Coalition's favour on last week.

The raw and LOESS charts follow.

The two-party preferred (TPP) vote share aggregation yields a result of 44.3 to 55.7. However, the movement in the aggregation over the final week is driven by a single polling house; the new Morgan multi-mode poll. As I look at the aggregation, I am not sure whether to discount last week's jump or this week's decline for the Government. As both the jump and the decline appear to be (at least in part) driven by movements in the Morgan poll, it could be argued they cancel each other out.

I remain vexed by the new Morgan poll. Morgan has not released a lot of information on their polling methodology, which makes it difficult to assess. One of my issues is the new Morgan series is looking a little bouncy (perhaps over-dispersed) for its sample size. Something to ponder.

The longer running narrative for 2013 has been a sizable collapse of support for the government between January and late March. While this fall in voter support has been arrested, the recovery needs to pick up from its currently glacial pace for Labor to be well placed come September 14.

Turning to the aggregated primary votes:

1 comment:

  1. I'm also keeping an eye on possible overdispersion in Morgan multi. Not much data yet but looking like something to watch for. It would be nice to have more methods details concerning the stability (or not) of the %age of the pool that is sampled by the various methods each time.

    Seems to me that proving polls to be overdispersed is harder than proving them to be underdispersed, since there will always be some level of bounciness above randomly expected fluctuation, as a consequence of both long-term moves in voting intention and also short-term movements up and down. So while it's easy to say when a poll is not bouncy enough, it's not so easy to say when it's too bouncy.

    I'm not sure what the background level of average week-to-week movement in voting intention even without sample noise would be or even how to get a firm and non-circular handle on it. I'm thinking it is probably less than half a point.