How Change Happens

by Cass R Sunstein

Published 9 April 2019
The different ways that social change happens, from unleashing to nudging to social cascades.

"Sunstein's book is illuminating because it puts norms at the center of how we think about change."—David Brooks, The New York Times

How does social change happen? When do social movements take off? Sexual harassment was once something that women had to endure; now a movement has risen up against it. White nationalist sentiments, on the other hand, were largely kept out of mainstream discourse; now there is no shortage of media outlets for them. In this book, with the help of behavioral economics, psychology, and other fields, Cass Sunstein casts a bright new light on how change happens.

Sunstein focuses on the crucial role of social norms—and on their frequent collapse. When norms lead people to silence themselves, even an unpopular status quo can persist. Then one day, someone challenges the norm—a child who exclaims that the emperor has no clothes; a woman who says “me too.” Sometimes suppressed outrage is unleashed, and long-standing practices fall.

Sometimes change is more gradual, as “nudges” help produce new and different decisions—apps that count calories; texted reminders of deadlines; automatic enrollment in green energy or pension plans. Sunstein explores what kinds of nudges are effective and shows why nudges sometimes give way to bans and mandates. Finally, he considers social divisions, social cascades, and “partyism,” when identification with a political party creates a strong bias against all members of an opposing party—which can both fuel and block social change.


Why policies should be based on careful consideration of their costs and benefits rather than on intuition, popular opinion, interest groups, and anecdotes.

Opinions on government policies vary widely. Some people feel passionately about the child obesity epidemic and support government regulation of sugary drinks. Others argue that people should be able to eat and drink whatever they like. Some people are alarmed about climate change and favor aggressive government intervention. Others don't feel the need for any sort of climate regulation. In The Cost-Benefit Revolution, Cass Sunstein argues our major disagreements really involve facts, not values. It follows that government policy should not be based on public opinion, intuitions, or pressure from interest groups, but on numbers—meaning careful consideration of costs and benefits. Will a policy save one life, or one thousand lives? Will it impose costs on consumers, and if so, will the costs be high or negligible? Will it hurt workers and small businesses, and, if so, precisely how much?

As the Obama administration's “regulatory czar,” Sunstein knows his subject in both theory and practice. Drawing on behavioral economics and his well-known emphasis on “nudging,” he celebrates the cost-benefit revolution in policy making, tracing its defining moments in the Reagan, Clinton, and Obama administrations (and pondering its uncertain future in the Trump administration). He acknowledges that public officials often lack information about costs and benefits, and outlines state-of-the-art techniques for acquiring that information. Policies should make people's lives better. Quantitative cost-benefit analysis, Sunstein argues, is the best available method for making this happen—even if, in the future, new measures of human well-being, also explored in this book, may be better still.