Getting consent to survey in new ways: evidence from experiments about questions by text message in the Understanding Society Innovation Panel

Some information cannot (reliably) be collected in annual surveys of panel members. Text messages (SMS) are well-suited to gathering time-sensitive responses, if a large and representative subset of a panel consents to being surveyed in this way. We investigate: (1) What proportion of respondents consent to text message questions? How does that vary by sample cohort, mode, and whether previously asked for consent? (2) What is the effect of consent question placement within the questionnaire? (3) Is bias of the covered sample reduced by re-asking non-consenters at a later wave? (4) What coverage of non-internet users is gained by seeking consent for text message questioning? We use data from experiments within two waves (IP13 and IP15) of the Innovation Panel of Understanding Society: the UK Household Longitudinal Study. Most respondents consented to receive questions by text message when first asked (69% in IP13, 74% in IP15). Of those who declined consent at IP13, 55% consented when re-asked two years later. Face-to-face respondents were more likely to consent than web respondents. Slightly more (2.4 percentage points, s.e.1.5 percentage points) respondents consented when experimentally asked late in the questionnaire than when asked early. Re-asking consent not only reduced the proportion of people who had not provided consent, it also reduced non-consent bias, measured across a range of socio-demographic characteristics. Some panel members who never use the internet have mobile phones and consent to receive questions via text message, so this may complement web surveying.