The Predictive Power of Subjective Probability Questions

This paper evaluates the predictive validity of stated intentions for actual behaviour. In the context of the 2017 Dutch parliamentary election, we compare how well polls based on probabilistic and deterministic questions line up with subsequent votes. Our empirical strategy is built around a randomised experiment in a representative panel. Respondents were either simply asked which party they will vote for, or were asked to allocate probabilities of voting for each party. The results show that for the large majority of the respondents, probabilities predict individual behaviour better than deterministic statements. There is, however, substantial heterogeneity in the predictive power of the subjective probabilities. We find evidence that they work better for those with higher probability numeracy, even though probability numeracy was measured eight years earlier