Election forecasting

Electoral Trends #1 – The Fragmentation of the West

December 5, 2025 By Nigel Marriott

Last month’s General Election in The Netherlands was won by a party with less than 17% of the national vote. Dutch voters, politicians and pundits are now discussing what this means for a governing coalition which is likely to take a number of months complete. For myself, the election was yet another data point showing the fragmentation of the electorate in the West is the key trend over the last 40 years. As yet, there is no sign of this trend coming to an end and what the future holds I cannot tell.

UK General Elections #9 – The 40-55 Channel

July 4, 2025 By Nigel Marriott

Voting intentions in Britain were remarkably stable for the first half of 2025. The last time the polls were this stable was 10 years ago in the run up to the 2015 General Election.

What’s that I hear you say? Have I not noticed the surge in Reform’s vote share from 20% to 30%? I have but I’m focusing on the 40-55 Channel which has been the defining feature of voting intentions for nearly all of the last 15 years. Everything I see in 2025 tells me the 40-55 Channel will continue to define British politics all the way through to the next election by 2029. Perhaps I better explain what I’m talking about.

UK Local Elections #2C – 2025 West England Mayoral Election – Review of My Forecast

May 6, 2025 By Nigel Marriott

Labour have retained the West of England Combined Authority (WECA) Mayoralty As I predicted, the contest was won with less than a quarter of the vote and with a small majority (less than 3%). Unfortunately, I had the Greens winning the mayoralty so on the face of it, this is a forecasting error for me. However, when voters are as fragmented as they are today, measuring forecasting skill is not as straightforward as it might seem.

UK General Elections #8 – How accurate are voting intention polls? – updated with GE2024

August 4, 2024 By Nigel Marriott

After their 2nd best ever performance in the 2019 UK General Election, the UK polling industry flipped in the 2024 UK General Election to their 2nd worst ever performance after 1992. 6 of the last 9 elections have seen at least one party experience a major polling error. It would appear the move to web polling and lower barriers of entry has led to poorer quality polls.

UK General Election 2024 #5 – My Final Forecast as of 3rd July 2024

July 3, 2024 By Nigel Marriott

My third and final forecast of the number of seats to be won by each party in the 2024 UK General Election is –

CON 130 (+17)
LAB 420 (-17)
LD 50
SNP 25
GRN 3
PC 2
REF 2
OTH NI 18

The numbers in brackets are the changes from my second forecast of 30th June 2024.

This article is based on polling data as of 2000 on 3rd July 2024. If more polling data comes in and causes me to change my forescript, the changes will be detailed in a postscript at the end of the article.

UK General Election 2024 #4 – My Forecast as of 30th June 2024

June 30, 2024 By Nigel Marriott

My second forecast of the number of seats to be won by each party in the 2024 UK General Election is –

CON 113 (+5)
LAB 437 (-5)
OTH 100 (unch)

The numbers in brackets are the changes from my first forecast of 23rd June 2024.

UK General Election 2024 #3 – My Forecast as of 23rd June 2024

June 23, 2024 By Nigel Marriott

My first forecast of the number of seats to be won by each party in the 2024 UK General Election is –

CON 108
LAB 442
OTH 100

UK General Election 2024 #2 – My Forecasting Model

June 22, 2024 By Nigel Marriott

My UK General Election 2024 forecasting model will be a top down version which I last used in 2010. Top down approaches first predict how many seats each party will win in total before seeking to identify which seats each party wins. This differs from the bottom-up approach I used in 2017 & 2019 where I forecast the outcome for each seat first and then aggregated the forecasts.

Here I explain how my 2024 forecast will be made but it finishes with a warning that I may have to dump my 2024 model in favour of the forecasting approach I used for the 2015 general election.

UK General Elections #7 – How accurate are voting intention polls? – Revised

June 8, 2024 By Nigel Marriott

Voting intention polls in the UK are accurate after all!

For years, I’ve observed that UK polls on average underestimate the Conservative vote and overestimate Labour’s vote. When I converted poll data into forecasts of seats won, I had to first estimate how much polling error there would be. So what’s changed? It turns out I was comparing polls to the wrong statistic, namely national vote share. The correct comparator is in fact average vote share per seat.

Voice Referendum #2 – My Forecast Reviewed

November 5, 2023 By Nigel Marriott

Australians rejected the proposed constitutional amendment known as The Voice in a referendum on 14^th October 2023. NO won the national vote by 20.1 percentage points and the state count 6-0 but the more important question is was my forecast right?