The illusion of evidence-based nudges

Author

Jason Collins

Published

August 1, 2024

From a recent Journal of Political Economy paper by Stefano DellaVigna, Woojin Kim and Elizabeth Linos (2024):

We study 30 US cities that ran 73 RCTs with a national nudge unit. Cities adopt a nudge treatment into their communications in 27% of the cases. We find that the strength of the evidence and key city features do not strongly predict adoption; instead, the largest predictor is whether the RCT was implemented using preexisting communication, as opposed to new communication.

A nudge with a negative result is almost as likely to be implemented as a positive result.

There is no difference in adoption for results with negative point estimates (25% adoption), results with positive but not statistically significant estimates (25%), and estimates that are positive and statistically significant (30%). The likelihood of adoption increases with effect size (measured in percentage points), from 17% in the bottom third to 38% in the top third, though this difference is not statistically significant at conventional levels.

My cynical take is that running trials with nudge units is cool. Despite more than a decade of nudge unit stories, behavioural insights is still a “shiny new thing” and are a way to say “we’re doing science” The hard work of implementing or scaling an intervention simply isn’t as sexy.

References

DellaVigna, S., Kim, W., and Linos, E. (2024). Bottlenecks for evidence adoption. Journal of Political Economy, 000–000. https://doi.org/10.1086/729447