So the world is much more correlated than we give credit to. And so we see more of what Nassim Taleb calls "black swan events" - rare events happen more often than they should because the world is more correlated.

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

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

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

"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.

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.

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.