How and why does the mode of data collection affect consent to data linkage

We use experimental data to examine why respondents are less likely to consent to data linkage in online than face-to-face interviews. We find that respondents are less likely to understand the data linkage request, less likely to process the consent request thoroughly, and more likely to be concerned about privacy and data security when answering online rather than in a face-to-face interview. Verbal behaviours of interviewers do not explain the mode effects, and neither do the devices respondents use to complete the web survey. Simplifying the wording of the consent request increases understanding of the request, but does not reduce the gap in consent rates between modes.