<\/p>\n
My Articles on the 2024 UK General Election<\/strong><\/span><\/h5>\n\n- The most accurate forecaster of the 2019 general election<\/a> – I was independently assessed as the most accurate forecaster beating even Sir John Curtice’s exit poll.<\/li>\n
- Keir Starmer’s Train to Downing Street<\/a> – My assessment in 2021 of what Labour needed to do to win the next election.<\/li>\n
- My election forecasting Track Record 2010 to 2024<\/a> – A list of all election forecasts I have made for General, European and Local elections, how I made them, how they turned out and what lessons I learned.<\/li>\n
- How Accurate are Voting Intention Polls (Revised)<\/a> – A recent article which explains why I now think the polls are accurate when before they would often underestimate the Conservative lead over Labour.<\/li>\n
- Going Beyond the Swing in 2024<\/a> – A preliminary look at the 2024 general election at the start of the year.\u00a0 I give probabilities for 10 specific outcomes.<\/li>\n
- My 2024 UK General Election Forecasting Model<\/a> – I use a top down forecasting approach based on the sum and difference in Conservative and Labour vote share to predict share of seats won.<\/li>\n<\/ol>\n
<\/p>\n
Data used in this article<\/strong><\/span><\/h5>\nAll polling data prior to April 2024 comes from Mark Pack’s invaluable Pollbase<\/a>.\u00a0 For data since April, I am using the BBC poll tracker<\/a>.\u00a0 For a summary of what the polls are saying at the time of this article, see this X\/Twitter thread<\/a>.<\/p>\nAll electoral data I display and use in this article comes from the House of Commons Research Library<\/a>.\u00a0 The PDF file I use most of the time is this one UK Election Trends 1918-2019<\/a>.\u00a0 I’ve created a spreadsheet GB General Election Data 1918-2019 – votes and seats<\/a> which contains all the data used to build my models.\u00a0 For clarity –<\/p>\n\n- Seat Share<\/strong> is the percentage of seats in Great Britain won by each party.<\/li>\n
- National Vote Share<\/strong> is the percentage of all votes cast in Great Britain for each party.<\/li>\n
- Average Vote Share<\/strong> (per Seat) is the average of the vote share in each British constituency the party stands in.<\/li>\n<\/ul>\n
I first explained the national and average vote share concepts in my article “How accurate are voting intention polls? – Revised<\/em><\/a>“.<\/p>\n <\/p>\n
Reminder of my forecasting model for 2024<\/strong><\/span><\/h5>\nI am using a top down model to predict total number of seats won by the major parties based on the sum and difference in the Conservative and Labour party average vote share per seat.<\/p>\n
![\"\"](\"https:\/\/marriott-stats.com\/nigels-blog\/wp-content\/uploads\/2024\/06\/GE24-Forecast-GB-20240623.png\")
<\/p>\n
Once I’ve estimated sum seat share CON<\/span>+LAB<\/span><\/strong> and seat share difference CON<\/span>–LAB<\/span><\/strong>, I will have two simultaneous equations which can be solved to estimate the percentage of the 632<\/strong> seats in Great Britain that will be won by the Conservative and Labour parties.\u00a0 I explain my model in full here<\/a>.\u00a0\u00a0For now, my model does not yet split seats won by other parties into the separate parties e.g. Lib Dems, SNP, etc.\u00a0 I am working on this and will include this feature when ready.<\/p>\nOne of the questions I have to resolve is which of the fitted lines in the above charts should I use.\u00a0 In fact I will be using simulation where each line has a certain probability of being chosen.<\/p>\n
For CON<\/span>+<\/span>LAB<\/span><\/strong>, the probabilities I’ve decided to use are –<\/p>\n\n- Black line 5%<\/strong> – it’s been over 30<\/strong> years since this was the fit hence the low probability<\/li>\n
- Green line 75%<\/strong> – the last 7<\/strong> elections have used this fit hence why I say it is the most likely<\/li>\n
- Brown line 20%<\/strong> – given the high probability of a new low for CON<\/span>+<\/span>LAB<\/span><\/strong> vote share, I am not convinced the green line will hold hence why I’ve given this a 1 in 5 chance of this occurring.<\/li>\n<\/ul>\n
For CON<\/span>–LAB<\/span><\/strong>, the probabilities I’ve decided to use are –<\/p>\n\n- Black line 25%<\/strong> – the last 3 elections have sat on this fit so it can’t be ruled out.<\/li>\n
- Green line 75%<\/strong> – the last 3 times where Labour kicked out a Conservative government with a big swing (1929, 1945, 1997<\/strong>) all sat on the green line.\u00a0 Polls are pointing to something similar in 2024.<\/li>\n<\/ul>\n
The most likely outcome is that both models use their green fitted lines.\u00a0 This is what I will use to illustrate my forecast.<\/p>\n
<\/p>\n
Reminder of how accurate the polls are<\/strong><\/span><\/h5>\n
<\/p>\n
Data used in this article<\/strong><\/span><\/h5>\nAll polling data prior to April 2024 comes from Mark Pack’s invaluable Pollbase<\/a>.\u00a0 For data since April, I am using the BBC poll tracker<\/a>.\u00a0 For a summary of what the polls are saying at the time of this article, see this X\/Twitter thread<\/a>.<\/p>\nAll electoral data I display and use in this article comes from the House of Commons Research Library<\/a>.\u00a0 The PDF file I use most of the time is this one UK Election Trends 1918-2019<\/a>.\u00a0 I’ve created a spreadsheet GB General Election Data 1918-2019 – votes and seats<\/a> which contains all the data used to build my models.\u00a0 For clarity –<\/p>\n\n- Seat Share<\/strong> is the percentage of seats in Great Britain won by each party.<\/li>\n
- National Vote Share<\/strong> is the percentage of all votes cast in Great Britain for each party.<\/li>\n
- Average Vote Share<\/strong> (per Seat) is the average of the vote share in each British constituency the party stands in.<\/li>\n<\/ul>\n
I first explained the national and average vote share concepts in my article “How accurate are voting intention polls? – Revised<\/em><\/a>“.<\/p>\n <\/p>\n
Reminder of my forecasting model for 2024<\/strong><\/span><\/h5>\nI am using a top down model to predict total number of seats won by the major parties based on the sum and difference in the Conservative and Labour party average vote share per seat.<\/p>\n
<\/p>\n
Once I’ve estimated sum seat share CON<\/span>+LAB<\/span><\/strong> and seat share difference CON<\/span>–LAB<\/span><\/strong>, I will have two simultaneous equations which can be solved to estimate the percentage of the 632<\/strong> seats in Great Britain that will be won by the Conservative and Labour parties.\u00a0 I explain my model in full here<\/a>.\u00a0\u00a0For now, my model does not yet split seats won by other parties into the separate parties e.g. Lib Dems, SNP, etc.\u00a0 I am working on this and will include this feature when ready.<\/p>\nOne of the questions I have to resolve is which of the fitted lines in the above charts should I use.\u00a0 In fact I will be using simulation where each line has a certain probability of being chosen.<\/p>\n
For CON<\/span>+<\/span>LAB<\/span><\/strong>, the probabilities I’ve decided to use are –<\/p>\n\n- Black line 5%<\/strong> – it’s been over 30<\/strong> years since this was the fit hence the low probability<\/li>\n
- Green line 75%<\/strong> – the last 7<\/strong> elections have used this fit hence why I say it is the most likely<\/li>\n
- Brown line 20%<\/strong> – given the high probability of a new low for CON<\/span>+<\/span>LAB<\/span><\/strong> vote share, I am not convinced the green line will hold hence why I’ve given this a 1 in 5 chance of this occurring.<\/li>\n<\/ul>\n
For CON<\/span>–LAB<\/span><\/strong>, the probabilities I’ve decided to use are –<\/p>\n\n- Black line 25%<\/strong> – the last 3 elections have sat on this fit so it can’t be ruled out.<\/li>\n
- Green line 75%<\/strong> – the last 3 times where Labour kicked out a Conservative government with a big swing (1929, 1945, 1997<\/strong>) all sat on the green line.\u00a0 Polls are pointing to something similar in 2024.<\/li>\n<\/ul>\n
The most likely outcome is that both models use their green fitted lines.\u00a0 This is what I will use to illustrate my forecast.<\/p>\n
<\/p>\n
Reminder of how accurate the polls are<\/strong><\/span><\/h5>\n
All electoral data I display and use in this article comes from the House of Commons Research Library<\/a>.\u00a0 The PDF file I use most of the time is this one UK Election Trends 1918-2019<\/a>.\u00a0 I’ve created a spreadsheet GB General Election Data 1918-2019 – votes and seats<\/a> which contains all the data used to build my models.\u00a0 For clarity –<\/p>\n I first explained the national and average vote share concepts in my article “How accurate are voting intention polls? – Revised<\/em><\/a>“.<\/p>\n <\/p>\n I am using a top down model to predict total number of seats won by the major parties based on the sum and difference in the Conservative and Labour party average vote share per seat.<\/p>\n Once I’ve estimated sum seat share CON<\/span>+LAB<\/span><\/strong> and seat share difference CON<\/span>–LAB<\/span><\/strong>, I will have two simultaneous equations which can be solved to estimate the percentage of the 632<\/strong> seats in Great Britain that will be won by the Conservative and Labour parties.\u00a0 I explain my model in full here<\/a>.\u00a0\u00a0For now, my model does not yet split seats won by other parties into the separate parties e.g. Lib Dems, SNP, etc.\u00a0 I am working on this and will include this feature when ready.<\/p>\n One of the questions I have to resolve is which of the fitted lines in the above charts should I use.\u00a0 In fact I will be using simulation where each line has a certain probability of being chosen.<\/p>\n For CON<\/span>+<\/span>LAB<\/span><\/strong>, the probabilities I’ve decided to use are –<\/p>\n For CON<\/span>–LAB<\/span><\/strong>, the probabilities I’ve decided to use are –<\/p>\n The most likely outcome is that both models use their green fitted lines.\u00a0 This is what I will use to illustrate my forecast.<\/p>\n <\/p>\n\n
Reminder of my forecasting model for 2024<\/strong><\/span><\/h5>\n
<\/p>\n\n
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Reminder of how accurate the polls are<\/strong><\/span><\/h5>\n
![\"\"](\"https:\/\/marriott-stats.com\/nigels-blog\/wp-content\/uploads\/2024\/06\/PollErrors4-GE19-avg-vote-share-Diff.png\")
<\/p>\n![\"\"](\"https:\/\/marriott-stats.com\/nigels-blog\/wp-content\/uploads\/2024\/06\/PollErrors4-GE19-avg-vote-share-Sum.png\")
<\/p>\n![\"\"](\"https:\/\/marriott-stats.com\/nigels-blog\/wp-content\/uploads\/2024\/06\/GE24-Polls-Summary-20240621.png\")
Labour has a 20<\/strong> point lead over the Conservatives.\u00a0 This would be a new record for Labour if this occurs on 4th July.<\/p>\n