If government is inevitable, the challenge is to come up with the most effective one possible.

When the rich build bigger, they shift the frame of reference that shapes the demands of the near rich, who travel in the same social circles. Perhaps it's now the custom in those circles to host your daughter's wedding reception at home rather than in a hotel or country club. So the near rich feel they too need a house with a ballroom. And when they build bigger, they shift the frame of reference for the group just below them, and so on, all the way down.

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 decry rising inequality because it makes those who've fallen behind feel impoverished. But it's done much more than cause hurt feelings. It has also raised the real cost to middle-income families of achieving many basic goals. The process begins with the completely unremarkable fact that top earners have been spending at a substantially higher rate than before. They've been building bigger mansions, staging more elaborate weddings and coming-of-age parties for their kids, buying more and better of everything.

All parents want to send their children to the best possible schools. But because a good school is a relative concept, a family cannot achieve its goal unless it outbids similar families for a house in a neighborhood served by such a school. Failure to do so often means having to send your kids to a school with metal detectors at the front entrance and students who score in the 20th percentile in reading and math. Most families will do everything possible to avoid having to send their kids to a school like that. But because of the logic of musical chairs, they're inevitably frustrated.

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.