Separating refusal bias and non-contact bias: evidence from UK national surveys

Refusal by sample units and failure to contact sample units can both contribute to survey non-response bias. However, the nature of the contribution can be rather different in the two cases. Extended field efforts may reduce either or both components of non-response bias. We examine data from several UK surveys on extended field efforts and the effect that they appear to have on non-response bias and its components. Some consistent patterns are found. We also explore the sensitivity of such analyses to the operational definition of extended efforts. The findings provide some evidence of the relative roles of refusal conversion and repeated contact attempts in reducing non-response bias. The study also has implications for the development of appropriate field strategies to combat non-response bias.