Dynamic norms drive sustainable consumption: Norm-based nudging helps café customers to avoid disposable to-go-cups

Excess use of disposable to-go-cups constitutes a severe sustainability threat. Behavioral economics and economic psychology suggest various antidotes. In the present paper, we report two studies – a large-scale intervention field study and an experiment – that constitute independent, pre-registered, and open replication attempts of a recently-introduced intervention procedure: dynamic social norms. We tested whether a dynamic norm, along the lines of “more and more customers are switching from to-go-cups to a sustainable alternative. Be part of this movement and choose a reusable mug” – can help café customers to avoid disposable to-go-cups. Data from a fourteen-week intervention experiment with a total of 23,946 hot beverages sold – 18,019 in disposable cups and 5927 in reusable mugs – suggest that a dynamic-norm intervention for sustainable consumption helps customers avoid disposable cups and increases their use of reusable alternatives by 17.3% (or 4.1 percentage points). A follow-up online experiment corroborates this pattern and shows advantageous effects of a dynamic norm relative to a no-norm control condition, a static norm, an injunctive norm, and a combination of static-and-injunctive norm. In light of inconsistent and, at times, failed or even reversed replication results for seminal social norms studies, the present pre-registered studies indicate that dynamic norms are an effective means to facilitate sustainable behavior. We discuss scientific and applied implications and avenues for future research.