The “nudge” school of behavioral economics shot to prominence in 2008 with a book of that name by Cass Sunstein and Richard Thaler. (Thaler went on to win a Nobel Prize for his contributions to the field.) Their theory: Policies that gently encourage — or nudge — people to make good choices can succeed better than legislative decrees. For instance, if we cleverly design a homeowner’s utility bill to show her that neighbors are using less energy, maybe she’ll act a little greener too. Nudge theory rocketed from academia to governments around the world because it seemed to offer a path to liberal outcomes, like better road safety, with none of the heavy-handed regulation that conservatives despise.