Now, modern economies have a very effective mechanism for deciding if salaries are really too high: it's called the free market. That's how most people's salaries are set, after all, including those of major-league baseball players and European soccer players.

Older people do a better job of managing their impulses, and so they're better able to put off putting off.

For a crowd to be smart, the people in it need to be not only diverse in their perspectives but also, relatively speaking, independent of each other. In other words, you need people to be thinking for themselves, rather than following the lead of those around them.

Breaking tasks down into smaller sub-tasks can be very useful.

From a social point of view, it's beneficial that homeownership encourages commitment to a given town or city. But, from an economic point of view, it's good for people to be able to leave places where there's less work and move to places where there's more.

The fact that cognitive diversity matters does not mean that if you assemble a group of diverse but thoroughly uninformed people, their collective wisdom will be smarter than an expert's. But if you can assemble a diverse group of people who possess varying degrees of knowledge and insight, you're better off entrusting it with major decisions rather than leaving them in the hands of one or two people, no matter how smart those people are.

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.