The effects of placement and order on consent to data linkage in a web survey

We report on an experiment in a supplemental web survey as part of a longitudinal study in the United Kingdom where we ask survey respondents to consent to two forms of data linkage to health records and to consent to be mailed a serology kit. We varied the placement (early, early in context or late in the survey) and order (linkage first or serology first) of the consent requests. We also examine reasons for consent or non-consent. We find that order of the requests does not make much difference, but making the requests early in the survey significantly increases consent rates over asking them after a series of content-related questions (by 3.4 percentage points) or later in the survey (by 7.2 percentage points). This is consistent with previous research showing that early requests for consent in a survey have a positive effect. The main reason chosen for not consenting related to the personal nature of the information requested.