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.

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.

The assumption that everybody will figure out how much they have to save and then will just implement that plan is obviously preposterous.

It turns out, that men, when they're taking care of their business, they're not fully attending to the task at hand, but, I'm sure there's an evolutionary explanation for this, if you give them a target, they will aim.

If people just put away what's left at the end of the month, that's a recipe for failure.

One simple step firms can take is make sure that people that are getting paid a lot of money, say more than a million or two, that a big chunk of that money is deferred. That's going to change the whole ballgame.

The lesson from behavioral economics is that people only save if it's automatic.