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

The same with the mortgage brokers that were selling people mortgages they couldn't afford. We shouldn't pay them on each mortgage they write. They should have what they call "skin in the game," where they've got to reimburse us if the guy who sold the mortgage defaults.

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.

LTCM lost money when Russia defaulted on a certain class of bonds, and then they had other investments like on the spread between two different kinds of shares of Royal Dutch Shell Oil Company. Now that seems completely unrelated to Russian bonds. But they were related because other hedge funds saw similar discrepancies and they were all making similar bets.

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.

Most people start claiming benefits within a year of when they become eligible, although benefits increase substantially if they wait.

A company invites their employees to sign up for a plan where every time they get a raise, some part of that raise goes to increasing their contribution rate to the 401k plan. In the first company we convinced to adopt this plan, saving rates tripled.