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.

Economics, as it is often taught today, portrays us as homo economicus-someone who doesn't vote in presidential elections, doesn't return lost wallets, and doesn't leave tips when dining out of town. Julie Nelson reminds us that most people aren't really like that. She helps point the way to a richer, more descriptive way of thinking about economic life.

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.

We've long known that firms can pay higher wages if they spend less on workplace safety enhancement. Libertarians ask, "If a worker is willing to accept higher wages in return for his agreement to exercise greater caution while performing his job, why should the government prevent him from making that choice?" It's a rhetorically powerful question, yet it overlooks the fact that the agreement in question will have adverse effects on others.

For the three decades after WWII, incomes grew at about 3 percent a year for people up and down the income ladder, but since then most income growth has occurred among the top quintile. And among that group, most of the income growth has occurred among the top 5 percent. The pattern repeats itself all the way up. Most of the growth among the top 5 percent has been among the top 1 percent, and most of the growth among that group has been among the top one-tenth of one percent.

We could curtail private spending by several trillion dollars a year without requiring painful sacrifices from anyone. That would be more than enough to rebuild our crumbling infrastructure and eliminate government indebtedness once and for all.

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.