In between the 2015 and 2017 General Elections, there were devolved Parliamentary and Assembly elections in Wales, Scotland and Northern Ireland.

Did the results of these prefigure any of the results, trends and changes seen in the 2017 General Election?


The 2017 General Election saw Labour gain 3 seats from the Conservatives, and Plaid Cymru gain one seat, Ceredigion, from the Liberal Democrats.

In terms of overall vote share, the trend was towards an increased two-party dominance. Labour and the Conservatives’ combined vote share in 2017 was 82.5%, up from 64.7% in 2015. Much of this increase came at the expense of UKIP, whose vote share declined from 11.2% to just under 2%.

Interestingly, few of these changes could be detected in the results of the Welsh Assembly elections, held in May 2016, seven weeks before the EU referendum. Labour and the Conservatives had a combined constituency vote share of just 55.8%, whilst UKIP and Plaid Cymru both increased their constituency share from the previous Assembly elections, to 12.5% and 20.5% respectively. (Welsh Assembly and Scottish Parliament elections have both a first-past-the-post, constituency vote system, and a proportional, regional vote system).

The Assembly and Westminster constituencies have the same boundaries, and mostly the constituency results were the same for both the 2016 and 2017 elections. Unlike at Westminster, the Liberal Democrats held Brecon and Radnorshire (which was held at Westminster in 2017 by the Conservatives), Labour held Vale of Glamorgan (which was held at Westminster in 2017 by the Conservatives) and Plaid Cymru held Ynys Môn (which was held at Westminster in 2017 by Labour).

The only constituency change in the 2016 Assembly elections saw Plaid Cymru gain Rhondda from Labour, with a 24.7% swing to Plaid compared to 2011. However, in the 2017 General Election, Labour increased its majority in the Rhondda constituency, with a swing of just over 9% from Plaid Cymru to Labour.

As the maps below show, although the 2016 Assembly results did not exactly match the 2017 Westminster results, they arguably prefigured some of the outcome, such as Labour winning back Gower and Vale of Clywd:


The SNP lost 21 of their previous 56 seats at the 2017 General Election, 12 of these to the Conservatives, 6 to Labour and 3 to the Liberal Democrats.

Scotland’s 59 Westminster seats and 73 Scottish Parliament constituencies are largely fought on different boundaries, which makes direct comparison more difficult. However, analysis of the 2016 Scottish Parliament elections did provide some indication of these trends, particularly the improved performance of the Conservative Party.

Whilst the SNP’s constituency vote share dropped in 2016 compared to 2015, it was by a smaller amount than the decrease between 2016 and 2017. However, the Conservative Party saw a fairly consistent increase from 2015 to 2016 to 2017.

There isn’t a consistent movement between the three elections for Labour.

The improved performance of the Conservative Party can be seen more clearly by looking at the regional results for the 2016 Scottish Parliament elections. Its largest regional vote share increases, compared to the previous 2011 Scottish Parliament elections, were in North East Scotland (+12.8%), South Scotland (+9.3%) and Mid Scotland and Fife (+8.7%).

10 of the Conservatives’ 12 gains in the 2017 General Election were of constituencies within these regions.

Northern Ireland

The main trend of the 2017 General Election were seat gains and an increased share of the vote for the DUP and Sinn Féin, with the UUP and SDLP losing all their seats and seeing their share of the vote decline.

The situation in Northern Ireland is more complex, as there were two elections for the Assembly between the 2015 and 2017 General Elections. Although the constituencies are the same as for Westminster elections, the voting system is different, as multiple members are elected and parties can put up multiple candidates.

Comparing the total first preferences by constituency in the 2016 and 2017 Assembly elections, with the 2015 and 2017 General Election results, we can see the Assembly elections prefiguring an increased two-party dominance:

Although there wasn’t a consistent rise or fall across the four elections, there was a general trend of an increasing DUP and Sinn Féin vote share, and a declining SDLP and UUP vote share. This is also apparent looking at electoral maps (the parties with the most first preferences in Assembly elections are marked as having ‘won’ the seat):

In the 2017 Assembly elections, the DUP and Sinn Féin were the winning parties in all the constituencies held by the SDLP and UUP at the 2015 General Election. This pattern was also seen in the 2017 General Election, with the SDLP and UUP losing all their seats. The 2017 Assembly results match the 2017 Westminster results, apart from the Independent, Lady Sylvia Hermon (who did not stand in the Assembly elections) holding her North Down seat.

Picture credit: Stormont by davesandford –  Creative Commons Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0)