When do default nudges work?

Nudging is a burgeoning topic in science and in policy, but evidence on the effectiveness of nudges among differentially incentivized groups is lacking. This paper exploits regional variations in the rollout of the Covid-19 vaccine in Sweden to examine the effect of a nudge on groups whose intrinsic incentives are different: 16- to 17-year-olds, for whom Covid-19 is not dangerous, and 50- to 59-year-olds, who face a substantial risk of death or severe disease. We find a significantly stronger response in the younger group compared with the older (11.7 vs 3.6 percentage point increase in our study period), consistent with the theory that nudges are more effective for choices that are not meaningful to the individual.