What if many people just don’t bother voting in this election? The polls may suggest a landslide victory for Labour, but the party is worried about the millions of people who still say they are undecided or may think a Labour victory is so certain they don’t need to vote. A look at the history of voter turnout – and what don’t-knows and non-voters are saying – suggests the party is right to be concerned.

The black line in the chart below shows the turnout in every general election conducted in Britain since 1918. The most striking feature is the huge dip in turnout that occurred in 2001. That year’s turnout of 59% was almost the same as in 1918 (when Britain was still on a wartime footing). That has implications for the current election and helps explain Labour’s biggest anxiety in the final phase of the campaign.

Turnouts in UK general elections 1918 to 2019:

The blue line in the chart shows the predicted turnout using the vote shares of the Conservatives, Labour and the Liberals/Liberal Democrats in these elections. This is created by using these measures in what’s called a regression model to predict turnout.

The idea is that if one or more of the parties have a very good campaign, that should raise the overall turnout. If, on the other hand, the party campaigns are boring and the outcome predictable, we should see a lower turnout.

For example, in the 1959 general election the incumbent Conservative prime minister, Harold Macmillan, won almost 50% of the vote by proclaiming that........

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