There are many challenges to data collection in survey interviews. In contacting respondents and gaining cooperation we have the challenge of (unit) non response; how can respondents best be approached to convince them to cooperate and how can we keep respondents motivated? To try to answer this latter question, our research is conducted in the CentERdata LISS-panel, a panel consisting of about 5000 households

representative of the Dutch speaking population. The design of the LISS-panel combines a probability sample and traditional recruitment procedure with online interviewing. A specialty of this panel is that people without Internet access are provided with the necessary equipment so that they are also able to participate in the panel. Respondents receive questionnaires each month, this way providing data on many dierent topics.

More speci cally, we will look at reasons given for not wanting to join the panel (we will both look at reasons falling in prede ned categories such as no time or not interested as well as code other reasons given, i.e., open answers). For those respondents who did join the panel we will investigate whether questionnaire topic in uences participation rate: both taking into account demographics and values people may hold. Does questionnaire topicn motivate certain groups of people to participate (e.g., elderly, immigrants, or people with certain values)? In addition, we will look whether some groups evaluate dierent questionnaires (i.e., topics) dierently when they answered the survey. Evaluation consists of questions about liking and difficulty of the questionnaires.