Publication type
Understanding Society Working Paper Series
Series Number
2025-14
Series
Understanding Society Working Paper Series
Authors
Publication date
July 8, 2025
Abstract:
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. For comparisons of subsets, the proportions consenting are reported along with test statistics for group differences. For the mixed-mode experiment, we report both as-treated and intention-to-treat values, as well as instrumental variable analysis to estimate the effect of mode distinct from selection effects. Bias is analysed via differences between proportions in categories in the overall sample and the covered sub-sample. Most respondents consented to 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 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 use mobile phones and consent to receive questions via text message, so this may complement web surveying.
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