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.

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.

The link between rational individual behavior and collectively desirable outcomes is extremely tenuous.

The fact that many private expenditures are mutually offsetting actually happens to constitute a remarkably good bit of fiscal news. Mutually offsetting spending patterns are wasteful in the same way that military arms races are. In such situations, if each party spends less, nothing is sacrificed, yet resources are freed up that can be put to much better uses.

The private sector is first of all much larger than the public sector. The waste we see in that sector does not result from the fact that people spend their money carelessly. Mostly, it occurs because what one family must spend to achieve its goals often depends heavily on what other families spend.

Unless we can act collectively, there would be no way to defend ourselves, no way to define or enforce property rights. We couldn't curb congestion or pollution or build and maintain public infrastructure.

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.