How The Economist is projecting results live on election night

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How can we predict election results? The answer largely depends on when you ask the question. If you ask before election day, the usual approach is to take a poll of the electorate and tally up their vote intentions. But what if you’d like to hazard a guess at the result on election night itself, after people have voted and before the final totals have been decided?

Media outlets often turn to a special type of survey called an exit poll for initial answers. The exit poll is designed to predict each constituency’s swing in voting habits relative to the previous election. By polling voters’ choices in a selection of hand-picked, nationally-representative polling places, data scientists can predict the outcome of the election. But although the exit poll is typically bang-on, it is not an infallible methodology, and it is unhelpful if one party is predicted to win a number of seats within the margin of error of a majority (roughly 326 seats). If an exit poll is wrong or an election is too close to call, analysts can find themselves waiting for many hours until the final result is known. …

How The Economist’s data team answered this surprisingly difficult question

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A picture worth two thousand lines of code

Every summer since 2015, The Economist has published a special supplement in its weekly newspaper called “The World If”, filled with marvellously insightful and entertaining hypotheticals. What if the Ottoman Empire had never collapsed? What if human cloning went mainstream? What if the world had open borders? Typically, the answers are just as speculative as the questions imply, but this year we have added an extra piece based on our own data analysis. …


G. Elliott Morris

Data journalist for The Economist

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