Introduction
With
just one day to go before the British public cast their vote at the
ballot box, the ground war is hotting up. This article examines the
current state of the polls in looking at both vote and seat shares,
before outlining the importance of campaigning for political parties in
the final day.
The State of the Polls
The
last few years in UK polling have seen more sophisticated techniques
being used to survey voters, with market research companies such as
YouGov leading the way in online methodology. The last few weeks have
also highlighted the variations in the methodology that pollster’s use,
with some political parties advancing their claim based on a few
percentage point differences that are likely to be the result of the
different methodologies used (telephone, face-to-face, and internet)
alongside margins of error that is factored into every poll.
Much has
also been made of the election forecasting model used by the American
statistician Nate Silver. Silver’s model correctly predicted the
winner of all 50 states and the District of Columbia in the race for
the 2012 United States Presidential election. In the same year,
Silver’s model was also applied to U.S. Senate races, correctly
predicting 31 out of 33 seats. Whilst the Bayesian statistics and
number crunching that Silver deploys are complex, the model’s power to
predict political phenomena are impressive. Researchers in fields such
as Economics and Political Science know how difficult it is to
accurately predict human behaviour and Silver’s model seems to buck
this trend.
Election Models
When
turning to current election forecasting models, compelling statistical
coverage and analysis is provided by Election Forecast
UK. The model that Election Forecast UK uses combines data provided
by YouGov with all publicly released national and constituency polls,
alongside historical election results, and data from the UK
Census.
Current
forecasts as of the 5th May show the Conservatives on 34.5% and Labour
on 32.2%. This is provided in Table 1 below. The Liberal Democrats are
on 11.7%, with UKIP on 11%, the Greens on 4.1% and the SNP on 3.8%. The
strength of the Election Forecast UK model is that it factors 90%
uncertainty levels into the equation, in non-stats language, this means
that there is substantial statistical uncertainty included in the
model. Still, these 90% uncertainty levels provide robustness checks in
showing lower and higher values for vote shares.
Table
1- 2015 UK Parliamentary Election Forecast: % Vote Share
(Election
Forecast UK)
This then
leads us to the question of how do the % vote forecasts translate into
seat shares in Westminster? The Conservatives have the highest amount
of seats with 281 estimated. Again, 90% uncertainty levels are also
provided. When turning to Labour, the model estimates the party as
having 267 seats- 14 short of the Conservatives. According to the
model, the SNP are on course for 51 seats, with the Liberal Democrats
on 26. The most striking change, is the translation of votes into seats
for UKIP, with the model predicting that the party will only gain one
MP in Westminster. Figures 1 and 2 graphically show the variation in
the % forecast vote and the translation into seats across time, whilst
including 90% uncertainty levels for the lower and higher
values.
Table
2- 2015 UK Parliamentary Election Forecast: Seat Share
(Election
Forecast UK) (5th May 2015)
Figure
1- 2015 UK Parliamentary Election Forecast: % Vote Share
(Election Forecast
UK) (5th May 2015)
Figure
2- 2015 UK Parliamentary Election Forecast: Seat Share
(Election Forecast
UK) (5th May 2015)
General Election Prediction
“Nate
Silver, the world’s most respected pollster, says that the
Conservatives will win the most seats, but no political party is likely
to have enough MP’s to form a majority.”
The
renowned pollster Nate Silver recently outlined the difficulty in
predicting the 2015 British General Election. Labour still lie behind
the Conservatives and the electoral threat posed by UKIP appears to be
dissipating. Current election forecasts outline that the Conservatives
will win the most seats but that this will not transfer into a
majority, with the high likelihood that there will be a hung
parliament. Silver also outlined how the ‘shy Tory’ factor must also be
considered and has been embodied by “the historical tendency for the Conservatives to do
better in the election than in the polls”. This therefore makes the
final day in the run up to the General election crucial, in terms of
the local ground war, the overall national campaign, and the core election issues for all political parties (for
an overview, see my TNS opinion article with Chris Hanley: “The 2015 British General Election: Core
Battlegrounds”.)
Therefore,
every vote counts and there is all is to play for in the ground war on
the final day of the election.
Note:
The author would like to acknowledge electionforecast.co.uk for
providing access to the data which has been referenced fully.