Show me the error in my workings.
Gladly.
GE 2015 ... Miliband ... 30.4% ... ^1.4% pp - Cameron 36.9% -
required further swing - 3.25%
GE 2017 ... Corbyn ... 40.0% ... ^ 4.0% pp - May 42.3% -
required further swing - 1.55%
GE 2019 ... Corbyn ... 32.1% ... v7.9% pp - Johnson 43.6% -
required further swing - 5.75%
GE 2024 ... Starmer ... 33.7% ... ^1.6% pp - Sunak 23.7% -
majority achieved by swing of 1.6%
Analysis.
In these last four elections, no party has achieved a popular vote majority.
GE2015. Cameron was surprised to win. He won by a small number of seats.
GE2017 required a further swing to Labour of just 1.55%. This result is the closest Labour got to a majority which was achieved under Corbyn with a swing of 4%. The narrative on the Conservative benches was that May had been ''an electoral disaster''.
GE2019 was atypical because UKIP stood aside to help Johnson, meaning electoral arithmetic is less simple. Although Johnson claimed a landslide, even with the help of Farage standing down his candidates, Johnson achieved just 1.3% more than May. Johnson's epic win compared to May even with the help of Farage was just 0.65%.
GE2024. Starmer's landslide win was 6.3% short of that achieved by Corbyn in 2017, and only 1.6% better than that achieved by Corbyn in 2019.
Conclusion.
Your summary is incorrect, mostly because the UK electoral system is broken. Majority votes do not translate into seats. The 2017 GE result translated as Conservatives winning 317 seats with 42.3% of the vote and Labour losing with only 262 seats for 40.0% of the vote.
By comparison Labour won under Starmer with 411 seats for just a 33.7% share of the vote.
The system ignores the ''will of the people'' in favour of a system prone to external influences, such as unequal population densities and the potential for electioneering, gerrymandering, and candidate fixing.
They say a country gets the government that it deserves. Under the UK's broken electoral system, this can never be true.