SSE/EFI Working Paper Series in Business Administration
No 2006:9:
Are all crowds equally wise? A comparison of political election forecasts by experts and the public
Lennart Sjöberg ()
Abstract: Four groups made forecasts of the outcome of the Swedish
Parliamentary election in the fall of 2006. They consisted of members of
the public, political scientists, journalists writing about domestic
politics in Swedish daily newspapers, and journalists who were editing
sections of readers’ letters in daily newspapers. They estimated, using a
12-step category scale, which percentage of the votes that they believed 7
parties would get in the election. Data were then obtained on the outcome
of the election, and on the two opinions polls closest in time to it. When
median forecast were compared across groups, it was found that the group
from the public was most successful in forecasting the outcome of the
election. This was in spite of the fact that the median error made by
individual members of that group was about 50 percent larger than the
median error made by members of other groups. The two polls were less
efficient than the group from the public and overestimated the span between
the incumbent government and the opposition by a factor of 2. The members
of the public and journalists showed some wishful thinking in their
forecasts. There were large and consistent individual differences in
forecasting ability. Men performed better than women, as did those who
expressed more interest and knowledge in politics.
Keywords: election forecast; experts; opinion polls; (follow links to similar papers)
32 pages, October 3, 2006, Revised September 8, 2008
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- This paper is forthcoming as:
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Sjöberg, Lennart, 'Are all crowds equally wise? A comparison of political election forecasts by experts and the public', Journal of Forecasting.
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