Testing the impact of overt and covert ordering interventions on sustainable consumption choices: a randomised controlled trial

Abstract

The production, transportation, storage, and waste of food products have a significant impact on the environment. We investigated whether displaying products in ascending order of their carbon footprint in an online supermarket environment can shift consumer choices towards more sustainable options. We also examined whether the effect of the ordering intervention differs when the ordering is overt, where information about the ordering is explicit, compared to when it is covert and participants are not told about the ordering. We conducted a three-arm parallel-group randomised trial using 1842 online panel participants from England, Wales, and Northern Ireland, who had previously shopped online. Participants shopped for a meal for two, choosing one product from each of six product categories in a simulated online supermarket environment. Six products were shown in a vertical list on each product category page. Products were randomly ordered for the control arm, whereas the products were ordered by carbon footprint in the covert and overt ordering arms. In the overt ordering arm, a statement was displayed in a box at the top of each product page about the ordering of the products. The primary outcome was whether one of the three most sustainable products was chosen in each product category. There was no effect of the covert ordering intervention on the probability of choosing more sustainable products compared with the control arm (OR = 0.97, 95% CI 0.88-1.07, p = 0.533). Furthermore, we could not reject the hypothesis that the effects of the covert ordering intervention and overt ordering intervention do not differ (p = 0.594). Analysis of the control condition showed that the positioning of products had no effect on choices, which may explain why re-ordering products also had no effect. In the overt condition, only 19.5% of people correctly answered that the products were ordered according to sustainability in a follow-up question, suggesting that they didn’t notice the statement.