Evidence for behavioural interventions looks increasingly shaky

WHEN economists at the University of Toronto started to tell undergraduates in 2014 how many hours’ extra work they needed to put in to boost their grades, they hoped it would encourage the students to work harder.

They didn’t. Instead, the students just began to expect the lower grades they received.

The university’s experience is frequently quoted as an example of “nudge” theory backfiring. Nudge, the fashionable face of behavioural economics that launched a thousand light-touch government policies, has soared in popularity since the 2008 book of the same name by Richard Thaler, an economist, and Cass Sunstein, a legal scholar.