Is there a market for somebody selling a credit card that helps people pay down their balances? I think the question is yes. But it would have to be sold by a bank that's really willing to invest in being a trusted partner with its consumers, because they will make less money on each consumer.

Retirement savings is probably behavioral economists' greatest success story. It is a prototypical behavioral-economics problem because saving for retirement is cognitively hard - figuring out how much to save - and requires self-control.

When an economist says the evidence is "mixed," he or she means that theory says one thing and data says the opposite.

When should we nudge and when should we shove, I think, it's a political judgment. Obviously in some situations we need shoves, we need laws. Fraud is against the law, murder is against the law, drunk-driving is against the law. We don't need just nudges.

Every American worker should be able to save for retirement via payroll deductions.

Everyone's lost a lot of money on their 401k plans. I've heard some people calling them 201k plans. So it's even more important to get people to be saving more for retirement. Behavioral economics has helped us learn a lot about how to do that.

There are cases when I can make myself better off by restricting my future choices and commit myself to a specific course of action.