Electoral Calculus

Electoral Calculus is a political forecasting website that attempts to predict future United Kingdom general election results. It considers national factors and local demographics.

Main features
Electoral Calculus was developed by Martin Baxter, who was a financial analyst specialising in mathematical modelling. The site includes maps, predictions and analysis articles. It has separate sections for elections in Scotland and in Northern Ireland.

Methodology
The site is based around the employment of scientific techniques on data about the United Kingdom's electoral geography, which can be used to calculate the uniform national swing. It takes account of national polls and trends but excludes local issues.

The calculations were initially based on what is termed the Transition Model, which is derived from the additive uniform national swing model. This uses national swings in a proportional manner to predict local effects. The Strong Transition Model was introduced in October 2007, and considers the effects of strong and weak supporters. The models are explained in detail on the web site.

Predictions
Across the nine general elections from 1992 to 2024, the site correctly predicted the party to win the most seats in all but one (1992). They also correctly predicted the outcome, that is, the party winning a majority or a hung parliament, in six elections (majorities in 1997, 2001, 2005, 2019, 2024; hung parliament for 2010).

Reception
In 2004, the site was listed by The Guardian as one of the "100 most useful websites", being "the best" for predictions. With reference to the 2010 United Kingdom general election, it was cited by journalists Andrew Rawnsley and Michael White of The Guardian. John Rentoul of The Independent referred to the site after the election.