How Does Length of Fieldwork Period Influence Non-Response? Findings from ESS 2 in Poland

In this paper we show how one method of increasing the response rate, i.e. an extension of the fi eldwork period, infl uences the structure of non-response and the differences between respondents and non-respondents. We used data from the Pilot Study and the Main Study for the European Social Survey, Round 2, and from follow-up studies conducted after each of those. The fi eldwork period of the Pilot Study was 11 days and the one of the Main Study was nearly 2.5 months. The follow-up study involved distributing a mail questionnaire to people who did not participate in the face-to-face survey (non-respondents). Extension of the fi eldwork period brought a relatively modest increase in the response rate. However, a comparison of differences between the respondents and non-respondents for a short and a long fi eldwork period demonstrated that those differences occurred in demographic variables and in opinion questions. We also compared the effect of the length of fi eldwork period on differences between the respondents and two categories of non-respondents: refusers and inaccessibles for other reasons. We did not fi nd any effect of the length of the fi eldwork period on differences between respondents and inaccessibles for other reasons, neither in socio-demographics nor in opinion questions. However, the effect did occur when we compared respondents and refusers.