Polling

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 Local Elections #2B – 2025 West England Mayoral Election – My Final Forecast

April 27, 2025 By Nigel Marriott

The West England Combined Authority (WECA) Metro Mayor election of 2025 will probably be won with less than a quarter of all votes cast. My analysis shows it is a 5-way marginal, the likes of which have never been seen before in England. All five parties have reasons to be optimistic but as of now, I and most other forecasters make the Greens favourites to win the 2025 WECA mayoralty. With an election this tight, the parties get-out-the-vote efforts will play a big part in the final outcome.

All forecasts, charts & tables are based on the latest polls as of 26th April 2025.

UK Local Elections #2A – 2025 West England Mayoral Election – My Initial Forecast

April 13, 2025 By Nigel Marriott

The West England Combined Authority (WECA) Metro Mayor election of 2025 will probably be won with less than a quarter of all votes cast. My analysis shows it is a 5-way marginal, the likes of which have never been seen in England before. Why no-one has polled WECA is a mystery because this is shaping up to be one of the most unpredictable elections I’ve ever seen.

My forecast puts the Greens first with 24% but it also puts Reform, Lib Dems & Labour just behind with each on 20% and the Conservative and Independent candidates bringing up the rear. I am using a weighted average of four models of which 2 have Labour winning, 1 has the Greens winning and the 4th model (with the highest weight) has Reform winning. That’s how unpredictable the election is and why we need a WECA specific opinion poll!

This article is based on polls as of 7th April 2025. My updated forecast based on polls as of 26th April can be found here.

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 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 #1 – My Forecast Explained

October 13, 2023 By Nigel Marriott

Australians will reject the proposed constitutional amendment known as The Voice in a referendum on 14^th October 2023. My forecast is for NO to win the national vote by 17 percentage points and win the state count 6-0.

This article was first published on 11th October 2023. My forecast then was for NO to win 16 points and the state count 6-0.

Coronavirus #2 – What sample size does Boris need to lift all restrictions?

April 2, 2020 By Nigel Marriott

April Fools day 2020 saw the hive mind of social media asking what the sample size should be to measure the extent of the Coronavirus in the UK. I could see that many people responding were reaching for standard methodologies which are usually are based on specifying a desired confidence interval. In doing so, they were overlooking a much more effective and relevant alternative based on the methodology of Acceptance Sampling, first developed by the US Military in World War 2.

UK General Elections #5 – How accurate are voting intention polls? – updated with GE19

December 29, 2019 By Nigel Marriott

After 3 general elections with severe polling errors, the UK opinion pollsters redeemed themselves in the 2019 UK General Election with their most accurate performance since 1955. I base this statement on data provided by Mark Pack who has systematically recorded every opinion poll published since 1945. The challenge now for the industry is to maintain this level of performance for the next election which may be easier said than done given that 5 out of the last 8 elections have experienced a major polling error.

UK General Election 2019 Voting Intention – Final Polls

December 12, 2019 By Nigel Marriott

Today, the UK votes in its 3rd general election in less than 5 years. After serious polling errors in the last 3 general elections, it is understandable that everyone is taking the latest figures with a lot of salt. As it stands today, the polls are telling us that the Conservatives recovered their 2017 standing but Labour are still behind their 2017 performance.