Supplementary materials to: What can we learn from open questions in surveys? A case study on non-voting reported in the 2013 German longitudinal election study

Open survey questions are often used to evaluate closed questions. However, they can fulfil this function only if there is a strong link between answers to open questions and answers to related closed questions. Using reasons for non-voting reported in the German Longitudinal Election Study 2013, we investigated this link by examining whether the reported reasons for non-voting may be substantive reasons or ex-post legitimations. We tested five theoretically derived hypotheses about respondents who gave, or did not give, a specific reason. Results showed that (a) answers to open questions were indeed related to answers to closed questions and could be used in explanatory turnout models to predict voting behavior, and (b) the relationship between answers to open and closed questions and the predictive power of reasons given in response to the open questions were stronger in the post-election survey (reported behavior) than in the pre-election survey (intended behavior).