Assessment of a knock-to-nudge recruitment strategy to improve participation in a telephone survey: evidence from the National Survey for Wales

Summary

Knock-to-nudge (KtN) is a recruitment method in which interviewers visit sampled households and encourage participation in a later non-face-to-face survey. Originally introduced during the COVID-19 pandemic, KtN has since been adopted by several UK surveys in the post pandemic context. Limited evidence suggests that it increases response rates and improves sample composition. However, its effects on data quality, substantive variables, participation in additional tasks, and the optimal number of KtN visits remain underexplored. Using data from the 2022-2023 National Survey for Wales, we examine KtN visits to non-responding addresses. We find that KtN stage in recruitment significantly increases response rates and improves sample composition by recruiting younger participants, respondents from non White British backgrounds, renters, individuals without formal educational qualifications, and residents from larger households. These gains are concentrated in the first KtN visit, suggesting diminishing returns from subsequent visits and that a single visit may be sufficient. KtN respondents differ in substantive answers, indicating improved representativeness but show higher item non-response, more “don’t know” responses and lower participation in additional online modules, suggesting lower engagement. Overall, KtN may be an effective recruitment tool if gains in participation and representativeness outweigh increased costs, operational demands and potential reductions in data quality.