Data-driven model for forecasting results of the UK 2017 General Election based on adjusted voting patterns from the 2015 election

1. Forecasting the 2017 UK Election
Data-driven analysis based on 2015 results
(Selection of possible scenarios)
Model version 1.1
26 April 2017

2. Set-up
Model based on 2015 results: first 3 places in each constituency in England, Scotland and Wales.
Excludes Northern Ireland (18 seats, contested by local parties)
Model forecasts changes in seats won/lost if votes are distributed differently in each constituency
v1 e.g. if UKIP lost 50% of its votes, each constituency with a UKIP candidate would have its
UKIP votes reduced by 50%. Those votes can either be allocated to other parties, or
unallocated (i.e. reduced voter turnout)
This version of the model just forecasts results based on changes in voting preference. Does not
predict the likelihood of the scenario.
Abbreviations:
SNP = Scottish National Party, only contests seats in Scotland
WNP = Welsh National Party (Plaid Cymru), only contests seats in Wales
Updates:
1.1: Wales scenario added
More details at http://joiningdots.com/2017/04/25/forecasting-the-
election

3. Results and trends from 2015, 2010 and 2005 elections
Seats in 2015 Seats in 2010
Despite 3x increase in votes,
UKIP won only 1 seat in 2015.
SNP gained most seats, from
Liberal Democrats and Labour.
Liberal Democrats lost most
seats, to SNP in Scotland and
to Conservatives in Wales and
South West.

4. Marginal seats: 35 with winning margin of less than 2%
Of 632 seats in England, Scotland and Wales, 452 (72%) are safe. The winner would still
have won in 2015 even if combined all votes of 2nd and 3rd place. 35 seats are marginal,
winning by less than 2%, and are evenly divided between the main two parties

5. Forecast: Conservative gain 5% from UKIP
Mostly affects marginal seats,
Conservatives win outright with
increased majority

6. Forecast: Labour gains 5% from UKIP
Mostly affects marginal seats,
no outright winner with
Conservative majority

7. Forecast: Labour gain all of UKIP votes
Even if Labour won all of UKIP’s votes, still
wouldn’t win outright without Conservatives
and/or SNP also losing votes

8. Forecast: How Labour could win an outright majority
A Labour win requires SNP as well as
Conservatives to lose a lot of voters

9. Forecast: Liberal Democrats recover third of votes lost in 2015 election
A recovery by the Liberal Democrats
could prevent Conservatives winning
an outright majority

10. Forecast: Liberal Democrats recover third of votes lost in 2015 election
A recovery by the Liberal Democrats
could prevent Conservatives winning
an outright majority

11. Forecast: What could happen in Wales? (1/2)
Only 4 seats changed party in the 2015 election. Conservatives
won 3 at the expense of Labour and Lib Dems.
3 seats are marginal, 2 of which changed parties in 2015.
12 seats are targets of which 8 are held by Labour. Of those 8,
7 have Conservative in 2nd and UKIP in 3rd.

12. Forecast: What could happen in Wales? (2/2)
If 7% of votes shift from UKIP and Labour, Conservatives
gain 6 seats and Labour lose 7 seats.
Potentially increasing their margin by 13 seats
If 7% of votes shift from UKIP and Conservatives, Labour
only gain 3 and Conservatives only lose 3.
Potentially reducing their margin by 6 seats
If 7% of votes change party...
From UKIP and Labour -> To: Conservative, Liberal Democrats and Plaid Cyrmu (WNP)
From UKIP and Conservatives -> To: Labour, Liberal Democrats and Plaid Cymru (WNP)