The Danish Twin Survey on Political Orientations and Behaviors

The Danish Twin Registry is the oldest nationwide twin registry in the world and hosts information on 75,000 twin pairs collected over the past 130 years (Skytthe et al., 2006). The twin survey examined here was conducted by the Danish Twin Registry and was fielded in the period from October 1, 2009 to March 1, 2010. It was administered as a web survey, and 6,707 invitations were sent out to twins aged between 19 and 39 years who had previously agreed to participate in survey inquiries. These two selection criteria were used to maximize response rates and potential retention rates in subsequent waves, as the survey is the first wave of a panel study. Because this survey is also the first online survey conducted by the Danish Twin Registry, we recruited respondents from a younger, and presumably more web-savvy, age group. In total, 3,616 persons answered the questionnaire (a response rate of 53.9%), and of those, 3,345 agreed to answer questions concerning political attitudes and behaviors, resulting in a response rate of 49.9%. Thus, only 7.4% of the survey respondents chose not to answer the political questions after having answered questions on health issues. Danish twins generally display a high willingness to participate in surveys concerning health issues and the Registry records participation rates between 72 and 83%, RECEIVED 17 October, 2011; ACCEPTED 01 December, 2011.