What is sludge? Comparing Sunstein's definition to others'

Thaler and Sunstein’s book Nudge revolutionised how behavioural science is applied to public policy, with a simple and yet broad recommendation to build decision environments in ways that make people better off, as judged by themselves (Thaler & Sunstein, 2008). This idea has been attractive to many policymakers and academics, as nudges only encourage certain choices, rather than mandate them (Sanders et al., 2018). The Behavioural Insights Team, originally set up by the UK Prime Minister David Cameron, did much of the early work implementing nudging in practice. Their ‘EAST framework’ emphasises how nudges could work by making preferred choices easy, attractive, social, or timely (Behavioural Insights Team, 2014). This early work by the Behavioural Insights Team gives pension auto-enrolment is an example of a nudge that makes things easy, and the provision of information about neighbours’ energy consumption is an example of a social nudge. Both of these nudges can help improve household financial health, and so should help to make many people better off. In recent years, both Thaler and Sunstein have turned to a logical extension of their original idea, by looking at ways that decision environments can be built to make people worse off. This problem of ‘sludge’ was covered by Thaler (2018) first, has been subject to multiple papers by Sunstein (Sunstein, 2018, 2020; Sunstein & Gosset, 2020), and formed a chapter of the latest edition of Nudge (Thaler & Sunstein, 2021). Here, I review Sunstein’s new book, Sludge: What stops us from getting things done and what to do about it, the longest work from either of these two authors on sludge.