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

There's a second component of a good savings plan, which is something that a colleague of mine called Schlomo Benartzi and I developed many years ago, that we call "save more tomorrow."

Most economists, including me, agree that longevity insurance would make sense for a lot of people.

In a typical 401k plan, when you first become eligible you get a big pile of forms and you're told, fill out these forms if you want to join. Tell us how much amount you've saved and how you want to invest the money. In, under automatic enrollment you get that same pile of forms but the top page says, if you don't fill out these forms, we're going to enroll you anyway and we're going to enroll you at this saving rate and in these investments.

I don't go by the ratings. I buy wine that tastes good. Statistically, anybody's ability to predict what will be a good wine a decade from now is limited.

I'm all for empowerment and education, but the empirical evidence is that it doesn't work. That's why I say make it easy.

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.