Forecast update: 1 May 2015

Forecast main 150501

Less than a week to go, and we still make Cameron and Miliband pretty much 50-50 to be Prime Minister.

In our polling average, the Tories stay on 34%, a point ahead of Labour, while UKIP are down a point to 13% and the Lib Dems are still on 8%.

There’s not much change in the forecast since Tuesday. Our model gives a 90% chance of a hung parliament, a 10% chance of a Tory majority and just a 0.2% chance of a Labour majority.

The Conservatives are likely to win the most votes (78% chance) and most seats (75% chance), but we only give them a 51% chance of being able to form a majority alone, with the DUP, the Lib Dems, or both.

We give Ed Miliband a 17% chance of being able to form a majority without having to rely on the SNP (with the Lib Dems, the Lib Dems and the DUP, or the Lib Dems, the DUP and the other left-wing MPs). The chances of a Labour-led government that is reliant on at least tacit support from SNP MPs is 32%, giving Miliband a 49% chance of ending up in Downing Street overall.

Our central forecast has the Conservatives winning 290 seats. If they could get the support of the Lib Dems’ 25 MPs and the DUP’s 9 (for a total of 324), that’d just be enough for the slimmest of majorities in this scenario.

 

Date of forecast: 1 May 2015
Days till the election: 6

Inputted current average poll shares
Con: 34%
Lab: 33%
LD: 8%
UKIP: 13%
Others: 12%

Forecast GB Vote Shares (with 95% Prediction Intervals)
Con: 35% (31% – 39%)
Lab: 32% (28% – 36%)
LD: 10% (6% – 14%)
UKIP: 12% (8% – 16%)
Others: 11% (10% – 13%)

Forecast Scotland Vote Shares (with 95% Prediction Intervals)
SNP: 48% (44% – 52%)
Labour: 27% (23% – 31%)

Forecast GB Seats (with 95% Prediction Intervals)
Con: 290 (250 – 333)
Lab: 258 (217 – 296)
LD: 25 (16 – 34)
SNP: 53 (45 – 57)
PC: 3 (2 – 3)
UKIP: 3 (3 – 4)
Grn: 1
(May not sum to 632 due to rounding of sums of probabilities.)

Central forecast: Con short of a majority by 33
(Criterion for majority now changed to 323 not 326, assuming Sinn Fein win 5 seats and do not take them.)

Probabilities of key outcomes
Con most votes: 78%
Lab most votes: 22%

Con most seats: 75%
Lab most seats: 25%

Hung Parliament: 90%
… with Con largest: 65%
… with Lab largest: 25%

Probabilities of predicted government outcomes:
(See here for explanations and assumptions)

Con majority: 10%
Con+DUP: 7%
Con+LD: 19%
Con+LD+DUP: 15%
Con largest, Lab+SNP+DUP+other left maj: 6%
Con largest, but Lab+SNP+other left maj: 12%
Con largest, but Lab+SNP maj: 6%
Lab largest, Lab+SNP maj: 8%
Lab+LD+DUP+SDLP+PC+Grn+Hermon: 7%
Lab+LD+DUP: 5%
Lab+LD: 5%
Lab+DUP: 0%
Lab majority: 0%

(Probabilities may not sum due to rounding)

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