This intelligence, or what I'll call "the wisdom of crowds," is at work in the world in many different guises. It's the reason the Internet search engine Google can scan a billion Web pages and find the one page that has the exact piece of information you were looking for. It's the reason it's so hard to make money betting on NFL games, and it helps explain why, for the past fifteen years, a few hundred amateur traders in the middle of Iowa have done a better job of predicting election results than Gallup polls have.

Publishers, naturally, loathe used books and have developed strategies to depress the secondhand market. They bring out new, even more expensive editions of popular textbooks every three to four years, in a classic cycle of planned obsolescence.

In the auto industry, there's one thing you can always count on: if a new environmental or safety rule is proposed, executives will prophesy disaster.

The stock market has an insidious effect on C.E.O.s' moods, because of its impact not just on their companies but on their own bank accounts.

Wall Street has come a long way from the insider-dominated world that was blown apart by the Great Depression.

Lower oil prices won't, by themselves, topple the mullahs in Iran. But it's significant that, historically, when oil prices have been low, Iranian reformers have been ascendant and radicals relatively subdued, and vice versa when prices have been high.

If army ants are wandering around and they get lost, they start to follow a simple rule:Just do what the ant in front of you does. The ants eventually end up in a circle. There's this famous example of one that was 1,200 feet long and lasted for two days; the ants just kept marching around and around in a circle until they died.