In my work as a behavioral economist, I’ve thought a lot about how nudges can drive lasting behavior change. In the domain of retirement savings, Nobel laureate Richard Thaler and I devised a program called Save More Tomorrow back in the mid-1990s that used nudges to help people make better decisions about their long-term financial future. That program invites employees to gradually increase their savings rate over time, and it has been a success: according to my latest estimates, it has boosted the savings rates of as many as 15 million Americans.