Political interest in Swiss probability-based political and social surveys

Political scientists often draw conclusions about political behaviour based on a single survey, usually a postelection survey. Besides political surveys, social surveys that include measures of political behaviour are also considered rich sources and are used by many political scientists. Probability-based surveys face the problem of unit nonresponse: they disproportionately sample individuals who are more politically engaged. This is known to be a problem not only in political surveys but also in social surveys. What we do not yet know is whether there is a difference between political and social surveys in terms of the share of politically interested respondents. The present study offers an examination of political interest in Swiss probability-based cross-sectional political and social surveys, drawing upon a rich data set combining the Swiss Election Study (Selects), the European Social Survey (ESS), and the Measurement and Observation of Social Attitudes in Switzerland (MOSAiCH). Our findings suggest that Selects is more likely to comprise citizens with higher levels of political interest than ESS and MOSAiCH, though the effect is only significant compared to the latter. We discuss the implications of these results for the accuracy of political behaviour estimates of these surveys.