Swedish pollsters miss the mark, experts say

As elections approach, Sweden is awash in opinion polls, but their reliability and the consequences of inaccurate predictions are under scrutiny. Political scientist Annika Fredén notes that these polls can exert a significant psychological influence on voters.

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It can have a psychological effect.

Comparing Sweden to countries like the UK and US, where election results are aggregated differently, Annika Fredén, an associate professor at Lund University, suggests Swedish polls are generally more reliable. However, she cautions that they are not perfect, and certain voter groups may be over or underrepresented. For instance, Dan Hedlin, a professor of statistics at Stockholm University, points out that the Green Party historically received higher poll numbers than their actual election outcomes.

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Compared to Great Britain and the USA, where election results from different constituencies are combined in a different way, Swedish measurements are more reliable.

Hedlin attributes this to the Green Party's past broad appeal. He explains that polling institutes often ask a follow-up question for undecided voters: "which party is closest to your preference?" If voters indicate the Green Party, they are counted as Green supporters. Conversely, the Sweden Democrats have experienced the opposite effect, with their sympathizers being less inclined to participate in surveys, leading to their underestimation. While institutes employ methods to counteract this, they are not always sufficient.

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If one goes back in time, the Green Party always received higher figures in opinion polls than they did in the election.

Typically, major Swedish opinion polls have a margin of error of about two percent, according to Hedlin. However, individual polls can exhibit larger margins. One poll last spring indicated the Liberal Party would surpass the four percent threshold to enter parliament after announcing their intention to govern with the Sweden Democrats. Later, Demoskop's polling methods faced criticism for using a self-recruited panel. The potential for polls to influence voter behavior is particularly relevant when many voters are undecided, especially if the poll suggests a party is close to or above a critical threshold.

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Institutes do not just ask the question: which party would you vote for if it were an election today? For those who do not know, the next question is: which party is closest to hand? If you then say the Green Party, you are counted as a Green Party member.