The effect of questionnaire length on survey response

Survey textbooks suggest that long questionnaires should be avoided, and a careful reading of the available empirical evidence confirms the negative effects of substantial length on both response rates and the quality of those responses which are obtained. Data is presented from a lengthy survey in Britain in 1987. Analysis of reasons for nonresponse to this survey suggest that length may indeed have been a significant disincentive to respond for many. However, no effect of length was found on item quality as measured by the number of responses given to open-ended questions. Unexpectedly, the variance in number of responses was greater when the questions were asked later in the questionnaire. The results are interpreted as resulting from the greater power that respondents gain as the survey proceeds.