Whatever problem you’re trying to solve, make sure you’re not just attacking the noisy part of the problem that happens to capture your attention.

Poverty is a symptom – of the absence of a workable economy built on credible political, social, and legal institutions.

Married people, for instance, are demonstrably happier than single people; does this mean that marriage causes happiness? Not necessarily. The data suggest that happy people are more likely to get married in the first place.

Isaac Bashevis Singer, who won the Nobel Prize in Literature, wrote across many genres, including children’s books. In an essay called “Why I Write for Children,” he explained the appeal. “Children read books, not reviews,” he wrote. “They don’t give a hoot about the critics.” And: “When a book is boring, they yawn openly, without any shame or fear of authority.” Best of all – and to the relief of authors everywhere – children “don’t expect their beloved writer to redeem humanity.

The growth of the Internet will slow drastically, as the flaw in ‘Metcalfe’s law’ – which states that the number of potential connections in a network is proportional to the square of the number of participants – becomes apparent: most people have nothing to say to each other! By 2005 or so, it will become clear that the Internet’s impact on the economy has been no greater than the fax machine’s.

Know that some people will do everything they can to game the system, finding ways to win that you never could have imagined. If only to keep yourself sane, try to applaud their ingenuity rather than curse their greed.

People are complicated creatures, with a nuanced set of private and public incentives, and that our behavior is enormously influenced by circumstances.

If it takes a lot of courage to admit you don’t know all the answers, just imagine how hard it is to admit you don’t even know the right question.

It is well and good to opine or theorize about a subject, as humankind is wont to do, but when moral posturing is replaced by an honest assessment of the data, the result is often a new, surprising insight.

Were writing Freakonomics, we had grave doubts that anyone would actually read it – and we certainly never envisioned the need for this revised and expanded edition.