A good school is a relative concept, and the better schools are located in more expensive neighborhoods. But when everyone bids more for a house in a better school district, they succeed only in bidding up the prices of those houses. As before, 50 percent of all children will attend schools in the bottom half of the school quality distribution. As in the familiar stadium metaphor, all stand, hoping to get a better view, only to discover that no one sees better than if all had remained seated.

When people bump up against one another in the course of pursuing their goals, it is in everyone's interest to resolve any resulting problems in the least costly ways possible.

John Stuart Mill believed that the only acceptable reason for government to limit a person's liberty was to prevent him from causing unacceptable harm to others. Mill was not a libertarian, but many libertarians are quick to cite this principle when arguing against a regulation that they oppose. And I believe most thoughtful libertarians are prepared to embrace something fairly close to Mill's harm principle. But accepting that principle implies accepting many of the institutions of the modern welfare state that libertarians have vigorously opposed in the past, such as safety regulation.

As economists have long noted, the puzzle is not that so few people vote, it's that so many do. After all, no individual's vote has ever tipped the balance in a presidential election.

In short both the things we feel we need and the things available for us to buy depend largely—beyond some point, almost entirely—on the things that others choose to buy.

Adam Smith's uncritically enthusiastic modern disciples portray his invisible hand theory as saying that market forces reliably harness selfish individuals to serve the common good. That's often true, but as Darwin recognized clearly, many traits that serve the interests of individual animals make life more difficult for larger groups.

Many social critics wag their fingers at what they perceive to be frivolous luxury spending. But that misses the point that consumption norms are local. It's not just the rich who spend more when they get more money. Everyone else does, too. The mansions of the rich may seem over the top to people in the middle, but the same could be said of middle-class houses as seen by most of the planet's seven billion people.