**Incompatible probabilities:**

- Pr(Lab majority) = 15% & Pr(Lab largest party) = 12% are not compatible.
- How can Lab have a bigger chance of a majority than being the largest party?

**Conflict of interest?**

*Someone got paid from CCHQ?*

**What about UKIP?**

- Seems odd that there's no mention of UKIP. Not convinced this is best use of regression ever.
- Does this include #UKIP causing Conservatives in marginal seats losing to Labour?
- No Ukip MPs?
- No serious prediction can be made without factoring in Ukip They will take Labour as well as Conservative votes
- This model is flawed as it takes no account of UKIP's rise in popularity (even allowing for a possible tail off at the GE).

**Prediction is implausible?**

- Forgive my scepticism. No-one has polled over 40% in an election for 12 yrs, and the Tories haven't for 21.
- those Con + Lab vote shares would be mirror of Blair vs Hague in 2001
- All 3 points seem logical and v probable.. but direction of travel seems too drastic to take seriously.

**This time is different because of the coalition**

- History of Tory incumbency barely relevant because Coalition are incumbents not Tories.
- Surely many historical precedents are not valid because we are in a unique situation - there will be no incumbent government defending its position. All parties will be campaigning on the basis of change.
- Nor does it allow for the fact that a significant number of unhappy Lib-Dem voters will be registering their dis-satisfaction with the Coalition & voting Labour. As Mike Smithson says, this will be a unique election. Such generalised models based on previous voting patterns are, therefore, unlikely to be correct.

**Are past polls a good guide to the future?**

- Interesting data, but why assume that past polls are a good guide?
- My preference wld be for "fundamentals" forecasts at this stage (economy, maybe PM approval)

**Is this the best forecast we can do?**

- is your view that this model provides the most accurate available forecast, or just that these factors produce it?

**Regional and constituency factors**

- How's that going to happen without any Tory seats in a city north of Birmingham?
- Also doubt past precedent is helpful either & believe Tories are losing the North as they lost Scotland
- You results suggest a Tory lead of less than 10% resulting in comfortable majority. Which seems unlikely
- boundaries used to favour Tories now favour Labour.

**Switching between parties**

- Secondly what is going to happen to the 2010 LD>CON switchers. In your model they seem to evaporate.
- Third point the detail from almost all polls shows that very little of current LAB support comes from CON converts.
- To what degree does the model take into account the point frequently made by Mike Smithson, that the loss of half the Lib Dem vote from 2010 has mostly gone to Labour, and there appears to be little sign that it will either go back to the Lib Dems, and very little sign that it will migrate to the Conservatives?

**Taking previous election result into account**

- Historical tendencies? Well you forgot the historical tendency that incumbent parties have only once increased their share of the vote since the 50s.. 40% for the Tories from a 2010 starting point of of 35%? What a crock of shite!
- You are not taking into account that the GE to Mid-term fall this parliament is less than historical data

The model doesn't directly take the prior election result into account. It should influence things indirectly but affecting the levels of support in the polls in the mid term. I will explore further whether it adds value beyond current polls. What is being suggested in the first comment is actually a model of forecasting without any polls at all. It seems odd to ignore the most current information. I'm just arguing that we should look at with the perspective of how polls in the past have corresponded with future election results.

Hi, Dr Fisher,

ReplyDeleteLooking at the paper, one thing that I was wondering was whether you've considered whether a normal distribution was appropriate? of course, it would always make a sensible starting point, but I do think that the argument and data both imply that a non-gaussian and skewed distribution might be more appropriate.

From historical results, it would appear that the probability of (for example) a greater than 46% score for the Conservatives would be less than a sub-34% score, given the current polls and results of recent elections. Similarly, a greater than 35% score for Labour would appear more likely than a sub-28% score, although each of these would be equally likely given a symmetrical Gaussian distribution (each about 1 standard deviation away from the mean forecast).

Given also that we know that the Lib Dem probability distribution has to be skewed (with the hard end imposed at 0%), this gives further support to the hypothesis that the probability distributions for all party vote shares around the mean could be both skewed and non-gaussian.

Unfortunately, I haven't got a clue how to suggest adjusting the probability distributions (choice of shapes or skewness, or even how to start choosing what to do there).