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.

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?

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.

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.

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

A good rule of thumb is to assume that everything matters.

Investors must keep in mind that there's a difference between a good company and a good stock. After all, you can buy a good car but pay too much for it.