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

Maybe you'll take the cash out. So a credit card company or a bank that goes into the business of saying we're going to be the broker, we're going to sell you a mortgage that you're going to be able to pay off, we're going to help you reduce your credit card debt, we're going to help you save for retirement, we're going to put you into mutual funds that have low fees rather than high fees.

So, what's a nudge? A nudge is some small feature of the environment that attracts our attention and alters our behavior.

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

It would be much more consumer friendly for them to beep you when you swipe your card that says, uh-oh you're over your limit, are you sure you want to use that?

Rip Van Winkle would be the ideal stock market investor: Rip could invest in the market before his nap and when he woke up 20 years later, he'd be happy. He would have been asleep through all the ups and downs in between. But few investors resemble Mr. Van Winkle. The more often an investor counts his money - or looks at the value of his mutual funds in the newspaper - the lower his risk tolerance.

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.