Benefits of increasing the value of respondent incentives during the course of a longitudinal mixed-mode survey

This paper explores the effects of increasing the value of survey incentives on response rates and fieldwork efforts using data from a large-scale randomised experiment embedded in wave 12 of a national probability-based longitudinal survey. We also investigate whether effects differ between previous-wave respondents, who were sent an unconditional incentive, and previous wave non-respondents, who were offered a conditional incentive. The treatment group received £20 incentives instead of the usual £10 received at previous waves and by the control group. The results show a positive effect of the increased incentive on response rates for previous wave non-respondents and that this effect is heterogeneous across certain subgroups. The positive effect on response rates could translate into reduced fieldwork efforts in a web and CAPI sequential design.