For the sixth wave of data collection, a responsive fieldwork design was implemented in the German sub-study of the Survey of Health, Ageing and Retirement in Europe (SHARE). We monitored several respondent characteristics, known from previous waves, in relation to response outcomes and implemented adaptations of procedures. However, the lowest response probability we observed was related to income item nonresponse in the previous wave. Respondents who gave no answer to the income question in the previous wave started with a much lower response probability than any other group and mostly remained low. Although it hence seems to be a group for which responsive measures are especially worthwhile, it is difficult to translate into effective measures during the course of the fieldwork or in preparation of a new wave of fieldwork without knowing more about the possible common cause of the income nonresponse in one wave and unit nonresponse in the next wave. For understanding more about the underlying common cause, we pursue three strategies:
First, we explore the extensive information available in SHARE about panel members and about the response process. By this, we tried to find out whether attrition is preceded by a pattern of never answering to income questions up to a certain wave, or whether the drop-out follows immediately after one wave of item nonresponse. Preliminary results show that the second assumption holds. Income non-responders drop out of the panel in an early stage.
Second, we thoroughly analyze the characteristics of this group of respondents to reveal a possible relationship with other types of item nonresponse and to answer the question to what degree the interviewer can be viewed as the common cause. Preliminary results show that it is not the oldest old or cognitively challenged sample members who do not report their income, but more the working population, home owners and respondents with good numerical abilities. The interviewer explains only a small part of the variance overall, but interviewer’s own attitude and expectations about income questions do show significant effects.
Third, we plan to interview a selection of these panel members about their reasons for not answering the income questions. In the presentation we will discuss the progress and welcome ideas on the practical implementation of this third strategy. In the end, the project will result in a proposal for better adapted strategies for this subgroup of respondents, to prevent them from dropping out.