Forecast update: 20 March 2015

Forecast main 150320

Labour and the Tories are still tied in our national polling average, with 33% each. UKIP remains on 14%, and the Lib Dems on 8%. All of the polls in our average were conducted before Wednesday’s Budget, with the exception of the latest YouGov one, so we’ll have to wait to understand what, if any, effect the Budget has.

With the new Scotland poll by Survation included, the SNP gain a point in forecast Scottish vote share: they now lead Labour 44%-30%.

The overall effect is a slighter weaker forecast for the Tories (as they’re running out of time to move ahead), but no real improvement for Labour.

Our model now gives the Tories a 73% chance of winning the most votes (down a touch from 74% last week), a 54% chance of winning the most seats (down from 55%) and just a 9% chance of securing a majority (down from 10%). Labour’s chances of a majority remain just 4%.

With the polls still deadlocked and just seven weeks to go, the chances of a hung parliament climb to their highest yet: 87%. We make the Conservatives very slightly more likely to be the largest party in a hung parliament, but give Ed Miliband slightly more chance of forming a government, thanks to the potential for him to call on SDLP, Plaid, Green or SNP MPs, or Lady Hermon, for support if he needs it.

Our central forecast has the Conservatives finishing on 34.3% of the vote to Labour’s 31.6%, but winning just 6 more seats: 284 to 278. This scenario corresponds to the “SNP kingmakers or wreckers” wedge of the pie chart above. (Note that although it’s our central forecast, our model only gives it less than a one-in-six chance of happening.)

Date of forecast: 20 March 2015
Days till the election: 48

Inputted current average poll shares
Con: 33%
Lab: 33%
LD: 8%
UKIP: 14%
Others: 12%

Forecast GB Vote Shares (with 95% Prediction Intervals)
Con: 34.3% (30% – 38%)
Lab: 31.6% (27% – 36%)
LD: 9.9% (6% – 14%)
UKIP: 13.0% (9% – 17%)
Others: 11.2% (9% – 13%)

Forecast Scotland Vote Shares (with 95% Prediction Intervals)
SNP: 44% (40% – 48%)
Labour: 30% (26% – 34%)

Forecast GB Seats (with 95% Prediction Intervals)
Con: 284 (240– 332)
Lab: 278 (232 – 320)
LD: 21 (13 – 33)
SNP: 41 (29 – 50)
PC: 3
Grn: 1
(May not sum to 632 due to rounding of sums of probabilities. Prediction intervals not yet available for UKIP, PC and Grn.)

Central forecast: Con short of a majority by 39
(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 largest: 54%
Lab largest: 46%
Hung Parliament: 87%
… with Con largest: 45%
… with Lab largest: 42%

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

Con majority: 9%
Con+DUP: 6%
Con+LD: 12%
Con+LD+DUP: 12%

Con largest, SNP kingmakers or wreckers: 15%

Lab majority: 4%
Lab+DUP: 5%
Lab+LD: 14%
Lab+LD+DUP: 10%
Lab+LD+DUP+SDLP+PC+Grn+Hermon: 9%
Lab+SNP: 4%

(Probabilities may not sum due to rounding)

Probs trend new

Shares trend

Seats trend new

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