Brexit and the 2017 General Election

Attitudes to Brexit played quite an important role in people’s voting decisions; percentage voting Leave is very strongly correlated with increase in the Tory vote share

To what extent did people’s attitudes to Brexit affect how they voted in the 2017 General Election? We won’t know for sure until rich individual-level data become available. But the various aggregate-level data that are available suggest they played quite an important role.

First, in the month or so leading up to the election, Brexit was the top-ranked issue in both YouGov’s Top Issues Tracker (~62%) and Ipsos MORI’s Issues Index (~48%).

Second, as Will Jordan has pointed out, the vote distribution by age for the 2017 General Election looks a lot more similar to the corresponding distribution for the EU referendum than to the corresponding distribution for the 2015 General Election:

Third, Lord Ashcroft found that, while only 7% of Conservative voters describe themselves as “resistant to Brexit”, 43% of Labour voters and 56% of Lib Dem voters describe themselves as such.

Fourth, as the chart below indicates, percentage voting Leave is very strongly correlated (r = .79, p < 0.001 ) with increase in the Tory vote share from 2015 to 2017. (Note that this chart is based on data from the Electoral Commission, the House of Commons Library, and Chris Hanretty. Only constituencies in England are shown, due to the presence of nationalist parties in Scotland and Wales. Results were not markedly different when using all constituencies.)

And, as the chart below indicates, percentage voting Remain is strongly correlated with (r = .72, p < 0.001) the difference between the increase in Labour vote share and the increase in Tory vote share. (This chart was produced in the same way as the one above.)

Brexit was not the only issue that affected people’s voting decisions at the 2017 General Election, but it does appears to have have played an important role. It will be interesting to see how the distribution of party support changes over the coming months, as the parties’ respective positions on Brexit become clearer.