"Save more tomorrow" is a nudge to help people do what they know they want to do, which is save more, but they can't bring themselves to save more now. Just like many of us are planning to go on diets next month, or maybe in two months, certainly not tonight.

Every American worker should be able to save for retirement via payroll deductions.

I think one lesson we have to learn is that there's a lot more risk than we're giving credit to, a lot more what economist calls systematic risk.

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

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.

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.

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