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.

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.

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.

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.

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.

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.

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.