The Understanding Society survey includes what is known as an 'Innovation Panel' sample (IP). This sample is used to test different methods for conducting longitudinal surveys. The results from the Innovation Panel provide evidence about the best way to conduct a longitudinal survey, which is of relevance for survey practitioners working on other studies, as well as influencing decisions made about how to conduct Understanding Society. This paper reports the experiments, methodological tests, and other new data collection carried out at wave 16 of the Innovation Panel (IP16) from June to December 2023.

IP16 employed a mixed-mode design: some panel members were allocated to first be invited to a web version of the survey (with face-to-face as a follow-up mode), while others were invited to face-to-face first (with web as a follow-up mode); in both cases, telephone interviews were used as the third attempted mode. IP16 also continued ongoing experiments on the impact of incentives.

As with prior waves, several other methodological experiments were included in the survey.

Survey methods experiments / evaluations were conducted on: how to measure worries about climate change; how to measure depression; the use of e-vouchers for unconditional incentives; how to encourage responses to the youth survey; how to obtain information about child development measures; the effects of incentives on respondents' participation in a study using a game-like app; and what effect a government logo on envelopes sent to existing panel members would have on response rates.

In addition, IP16 was used to try out new survey content. New content was carried related to: what constitutes an interesting effect size when measuring people's psychological state; people's expectations of gender discrimination related to work; the extent and nature of the use of domestic workers, and how people find such workers; numeracy and the long-term future; the extent to which working flexibly is stigmatised; judging the passage of time; and associations between cognitive reflection abilities and politically motivated reasoning.

Other new data was gathered as part of IP16 and is presented in this paper relating to: child development measures from children's 'red book' records; and spatial navigation ability data from a game-like app.