Expert Predictions of the 2017 General Election: a survey

The U.K. Political Studies Association today released the results of its survey of expert predictions of the 2017 general election. The survey was distributed to members of the Association as well as a large number of survey researchers from major polling companies in Britain and to journalists from the print and broadcast media. Fieldwork was conducted between May 16th and 26th. The vast majority of responses were given before the launch of the Conservative manifesto and so at a time when the opinion polls were pointing to a 17 point Conservative lead over Labour.

We asked respondents to share their predictions of the vote shares for each party, the number of seats won, the probability of a Conservative majority of more than 100 seats, and the level of turnout.

• The prevailing view among our respondents at the time was that the Conservatives will secure a large majority, with an implied probability of 65% that they will win a majority of more than one hundred seats.
• The average prediction of the vote share for the Conservatives was 43%, while the share for Labour was 29%, an implied Conservative lead of some 14 points – well above the current polling average. The predicted share for the Liberal Democrats was 12%, 5% for UKIP and 4% for the Greens.
• There is a prevailing view that the Conservatives will end up as the largest party in parliament: the average prediction suggested that the Conservatives would win 371 seats, Labour 186 seats, the Lib Dems 16 seats and the SNP 47.
• The average predicted turnout for the election was 63%, which would be below the 66% turnout at the general election in May 2015 and far below the 72% achieved at the EU referendum.

The results of this survey should be interpreted in light of the political surprises of 2015 and 2016, and poor forecasting performance of similar expert surveys of predictions for the 2015 general election and the 2016 EU referendum. On those occasions the average respondent expected a close result between the Conservatives and Labour, and a narrow victory for Remain. Last year the experts did at least on average give Leave a 38% chance of winning.