Fifth combined forecast for the 2019 general election

By Stephen Fisher, John Kenny and Rosalind Shorrocks 

Since our update last week there have been several new forecasts, most notably including the YouGov MRP (multilevel regression and post-stratification) model. That was a nowcast rather than a forecast, but the same is true of most of our “forecasts”. More on differences between forecasting models below, along with some observations about intriguing question wording effects for citizen forecasts.

But first, overall, the seats projections overall have tightened for the Conservatives, who are down from a 353 average last week to 346 this week, while Labour are up from 209 to 218. The Liberal Democrat forecast total has dropped yet again (from 23 to 19). Now they are estimated to return fewer MPs than they had going into the election (20), but still more than the number of seats they won in 2017 (12).

Seats Betting Markets Complex models Simple models Average
Con 343 347 348 346
Lab 220 218 217 218
LD 19 18 19 19
Brexit 0 0 0
Green 1 1 1 1
SNP 45 45 44 45
PC 5 4 3 4
Con majority 36 45 46 42

Conservative Seats - 4th December

There is now remarkably little difference between the betting markets, complex and simple models in the expected size of the Conservative majority. Particularly striking is that on average the complex models differ by only a seat for each party from the simple uniform change projections based on the average of the opinion polls.

Continue reading Fifth combined forecast for the 2019 general election

Fourth combined forecast for the 2019 general election

By Stephen Fisher, John Kenny and Rosalind Shorrocks 

There has not been much change in our combined forecast over the last week. The Conservatives are still apparently headed towards a comfortable majority (55 on average) based on an average forecast vote share lead over Labour of 12 points. The average predicted probability of a Tory majority has crept up to 72%, partly due to increasing confidence in the betting markets and the quantitative forecasting models, as well as the polls. Citizens remain much more sceptical. Concerns that the Liberal Democrats might make little advance continue, and were compounded by the Datapraxis MrP forecast of just 14 seats for the party. Otherwise the Datapraxis forecast was largely in line with other forecasts of headline seats totals. Further MrP based forecasts are due this week, including YouGov’s.

Seats Betting Markets Complex models Simple models Average
Con 346 353 360 353
Lab 210 212 204 209
LD 25 21 22 23
Brexit 0 0 0
Green 1 1 1 1
SNP 45 45 43 44
PC 4 4 4 4
Con majority 42 55 69 55

Conservative Seats - 27th November   Continue reading Fourth combined forecast for the 2019 general election

Third combined forecast for the 2019 general election

By Stephen Fisher, John Kenny and Rosalind Shorrocks 

Once again all three sources of seat forecasts suggest the Conservatives are heading to a comfortable majority, while Labour are on course for a result on par with their previous post-war low of 209 seats in 1983. The Liberal Democrat forecast has been dropping steadily, so that they are now expected to end up with only a few more MPs than the twenty they had when they chose to support the election.

Seats Betting Markets Complex models Simple models Average
Con 346 354 363 354
Lab 209 211 200 206
LD 30 22 22 25
Brexit 0 0 0
Green 2 1 1 1
SNP 46 46 44 45
PC 4 4 4 4
Con majority 42 58 75 58

Con seats 20 NovLib Dem seats 20 Nov 

Continue reading Third combined forecast for the 2019 general election

How did the election forecasts do in 2017?

By Stephen Fisher, Rosalind Shorrocks and John Kenny.

Lots of the forecasts for the 2017 British general election were wrong in pointing to a Conservative majority. Most even suggested an increased majority when the party actually lost one. The well-known exceptions are the exit poll and YouGov multilevel regression and post-stratification (MRP) model. Less commonly remembered are the polls that were within a point of the Conservative-Labour lead and so, by standard uniform change calculations, provided an indication that the Tory majority was in jeopardy.

During the election campaign we ran an exercise combining the different forecasts for shares of the vote, seat tallies, and probabilities of a Conservative majority. Inevitably the combined forecast is only as good as the average of what goes into it, and that average was poor. But since the exercise involved classifying and averaging forecasts by the methodology they used, it is possible to reflect on which types of forecasting method performed better than others.

The figure below shows predictions of the Conservative share of the vote over the course of the campaign from the Political Studies Association (PSA) expert survey, betting markets, forecasting models and opinion polls. Strictly speaking polls are snapshots not forecasts, but the final polls performed as well as the experts and better than all the other methods. Consistently the worst source of predictions for the Tory share were the betting markets.

Conservative Vote Share 2017Note: Due to an error in our 2ndJune 2017 betting market calculation (and no way of correcting it at this stage) the betting market line runs direct (interpolates) from 26thMay to the final 8thJune 2017 estimate.

Continue reading How did the election forecasts do in 2017?

Second combined forecast for the 2019 general election

By Stephen Fisher, John Kenny and Rosalind Shorrocks

There are still just a few different forecasts for the general election. Perhaps the big changes during the 2017 campaign have made people more hesitant about predicting early this time. Perhaps the problems of the polls in 2015, 2016 and 2017 have put some off the idea entirely. (More on this in our post-mortem for the 2017 combined forecast which we’re still working on.) Nonetheless, this is the second of our weekly blogs where we review the different forecasts from different methods and combine them into an overall forecast.

Here we aggregate seats and vote share forecasts from a variety of sources including betting markets, polls, statistical forecasting models and citizen forecasts. As well as updating weekly, the methodology (as detailed below) might well evolve. So comments and suggestions on our approach and for new forecasts to include are welcome.

Just as they did last week, all the different sources point to the Conservatives being comfortably the largest party, with heavy losses for Labour and modest gains for the Liberal Democrats and Scottish National Party (SNP). Last week the betting markets suggested a smaller Tory tally than did the forecasting models. The models haven’t changed much but the betting markets have moved into line with forecasts. On average across betting markets, and complex and simple models, the Tories are expected to win with a comfortable majority of 60, barely changed from 57 last week. All three sources now suggest a majority of 50 or more.

Seats Betting Markets Complex models Simple models Average
Con 352 360 353 355
Lab 210 201 193 201
LD 37 25 30 31
Brexit 0 0 0
Green 2 1 1 1
SNP 46 48 50 48
PC 5 4 4 4
Con majority 54 70 56 60

Conservative Seats - 13th Nov

Continue reading Second combined forecast for the 2019 general election

First combined forecast for the 2019 general election

By Stephen Fisher, John Kenny and Rosalind Shorrocks (Universities of Oxford, Southampton and Manchester respectively)

There aren’t so many different forecasts for the general election out yet, but enough to start looking at how they compare. This is the first of hopefully weekly blogs where we review the different forecasts from different methods and combine them into an overall forecast. At the moment, the polls and seats forecasts suggest a comfortable Conservative majority but citizens and betting markets are not so sure it will happen.

The idea of combining forecasts from different sources has a good track record, though it has to be admitted that our attempts for the 2017 general election and the 2016 Brexit referendum did not work out well. We will write more about those experiences soon. Also worth noting is the experience of the pollyvote.com combined forecast of the US presidential elections.

Here we aggregate seats and vote share forecasts from a variety of sources including betting markets, polls, statistical forecasting models and citizen forecasts. As well as updating weekly, the methodology (as detailed below) might well evolve. So comments and suggestions on our approach and for new forecasts to include are welcome.

Continue reading First combined forecast for the 2019 general election

Leavers united could easily thwart divided Remainers

This is a longer and more detailed version of a post that was originally published by Prospect here on Friday. The opinion polls published over the weekend do not collectively show any substantial change from the figures in the table below.

By Stephen Fisher, 9th September 2019.

The government has lost its majority in parliament, so it is unlikely to be long before there is a general election. Already at the last election, the Conservatives attracted most Leave voters while Labour was most popular among Remain voters. So what has changed in the party preferences of Leave and Remain voters, and with what implications for the next election?

The Conservatives lost many of their Leave voters to the Brexit Party at the European elections earlier this year largely because of the government’s failure to deliver Brexit on schedule at the end of March. At the same time, frustrated with the complexity and ambiguity in Labour’s position on Brexit, many Labour Remain voters switched to the Liberal Democrats or Greens.

Since May (the month and the leader) the challenger parties have waned and the two main parties have recovered somewhat, but Westminster-vote intentions are still closer to the multi-party competition we saw in the Euro elections than they are to the two-party dominance of the 2017 election.

The table shows how Leave and Remain voters from 2016 voted in 2017, and how they intend to vote now. The changes show that the rise of the Liberal Democrats and Greens has been largely confined to Remain voters, while the Brexit Party has, unsurprisingly, only really attracted those who voted Leave in the referendum.

Table: 2017 vote and current vote intention, by 2016 vote

  2017 2019 Change
  Leave Remain Leave Remain Leave Remain
Con 63 25 52 16 -11 -9
Lab 25 53 12 37 -13 -16
LD 3 12 4 32 +1 +20
UKIP/Brexit 4 0 27 1 +23 +1
Green 2 3 1 7 -1 +4
             

Note: 2017 figures come from the British Election Study Internet panel. 2019 figures are the average of the most recent poll from each of Deltapoll, Opinium, Survation and YouGov taken between 21 August and 3 September 2019. The UKIP/Brexit row shows figures for UKIP from 2017 and the Brexit Party in 2019, and the change between the two. 

What is perhaps more surprising is just how both main parties have suffered setbacks among both Leave and Remain voters. Labour have fallen back almost as much among Leave voters as they have among Remain voters. While the largest outflow from Labour in absolute numbers is that among Remain, in relative terms, it is the other way round. Labour have lost just under a third of their 2017 Remain voters, but as much as half of their former Leave voters. As a result, Labour supporters are even more predominately on the Remain side than they were in 2017. Continue reading Leavers united could easily thwart divided Remainers

Election analysis and forecasting