In Defence of Liberty

Driven by data; ridden with liberty.

Local Elections 2017: Performance

Tomorrow, people from across the country will go to vote for seats in selected English local councils, in mayoral contests, and in Scottish and Welsh local government elections.

This article considers performance measures for the main parties.

Net Councillors Gained

One measure is to look at the gains and losses of councillors across the various councils, and to calculate the net gain in seats.

Professor Colin Rallings and Professor Michael Thrasher, of the University of Plymouth’s Election Centre, are responsible for an entire field of British psephology: the collection, study and analysis of local elections data.


As part of their work, they use local by-elections in principal authorities to estimate the numbers of councillors gained or lost, on net.

These predictions apply to English local authorities.

Their first prediction had the governing Conservatives gaining 50 councillors, and Labour losing 50.

Their revised prediction has Labour losing 75 net councillors, with the Conservatives gaining 115.

If either prediction holds, this would be atypical performance for HM’s Most Loyal Opposition, who usually gain seats in local elections.


Professor Rallings and Professor Thrasher also calculate what would happen if local elections were being held across Great Britain, with the main three (or four) parties standing in each ward. This national equivalent vote share (NEV) is published in the Sunday Times.

Their revised prediction for the 2017 local elections NEV is for the Conservatives to win on 35% (up 9 points versus 2013), and Labour to be on 29% (the same as in 2013).

There is a similar calculation, called the projected national share (PNS), conducted by Professor Curtice and Professor Fisher. The similarities and differences of these measures is considered in a previous article.

Not a Guide

Given the new mayoral elections, and electoral performances in Scotland and Wales to look out for, these elections are interesting in of themselves.

Neither the PNS nor the NEV should be taken as a strict guide as to what will happen in the upcoming general election on 8th June 2017.

As in 2017, the general elections of 1983 and 1987 were held in June after local elections in May.

AW local vs general 1983 and 1987-01

As Anthony Wells, of YouGov, says:

However, don’t just assume that the projected overall shares of the vote at this week’s votes are going to be repeated in next month’s election: people vote differently for different reasons at different sorts of election.

As counting and declarations will be made throughout Friday, we have to wait and see how each party performs against their past and predictions.


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This entry was posted on May 3, 2017 by in Local Politics and tagged , , .
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